Title: CCNA
Tags: Configure OSPF IPv6 EIGRP STP Router OSI FrameRelay WAN Ports VLAN Protocol VPN HSRP Cabling VTP Etherchannel Licensing PPP RIP TCPIP ACL GLBP NAT SNMP Ethernet Netflow DHCP ISDN PortSecurity

Front: OSI 7 layers
Back: all people seem to need domino's pizza
7 application
6 presentation
5 session
4 transport
3 network
2 data-link
1 physical

Front: OSI layer that Routers work on
Back: Network layer, layer 3

Front: 2 subdivisions of Data-Link layer
Back: LLC Logical link control - talks to Network layer
MAC Media access control - talks to Physical layer

Front: PDUs for each layer of the OSI model
Back: PDU: Don't don't don't stop pouring free beer.  (data data data segments packets frames bits)
Protocol Data Unit

Front: 3 layers of Cisco 3-layer model
Back: Core - Main router.  need speed, redundancy
Distribution - does majority of work, most routing decisions. contains NAT, vlans, policy-based routings, firewall, etc.
Access - an extension of the distribution layer

Front: TCP/IP suite - 2 components
Back: TCP/IP suite - TCP Transmission Control Protocol and IP Internet Protocol.  TCP: connection-oriented: handshake, sequencing, etc.  IP: connectionless

Front: CSMA/CD acronym expansion and basic definition
Back: Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
Media access control method used most notably in local area networking using early Ethernet technology. It uses a carrier sensing scheme in which a transmitting data station detects other signals while transmitting a frame, and stops transmitting that frame, transmits a jam signal, and then waits for a random time interval before trying to resend the frame.[1]

Front: 568A and B cable colors
Back: Color determines the pair: Blue=1, Orange=2, Green=3, Brown=4. Blue sky, Orange sun rising, shine on Green Grass, and Brown dirt.
A: 1 center, 2 around center, 3 left, 4 right.  Solid on the right, except for the center.  :-D
B switches pairs 2 and 3 (orange and green) - B is 1324

Q: Crossover cable has [...] standard on each side.  Used to connect [...] items.
A: different; similar

Q: 568A cable colors
A: 1 = Blue, 2 = Orange, 3 = Green, 4 = Brown
blue sky, orange sun rises, green grass, brown shit
568B swaps 2 and 3

Q: Rolled cable color
A: uses the 568B colors, then mirrored.
Note 568B pairs are: 1 in the middle, 2 left, 3 around middle, 4 right
Blue = 1, orange = 2, green = 3, 4 = brown (blue sky, orange sun, green grass, dirt)

Q: 5 things needed to communicate from one node to another
A: need source IP, source MAC address, dest IP, dest MAC address, and port

Q: OSI application layer: what does it do, what is its PDU, what protocols?
A: PDU = DATA; accesses the network to see if it's ready to receive the info.  HTTP, FTP, SMTP, TELNET, SSH, DNS, SNP, NTP etc"

Q: Presentation layer: what does it do, PDU?
A: PDU = DATA, presents things to the app layer.  ascii, encryption, delivery and formatting.

Q: All IPv4 Address classes, 1st octet, and default subnet
A: A starts at 1, B starts at 128, C starts at 128+64 = 192, D starts at 192+32 = 224, E starts 224 + 16 = 240
class; 1st octet; Default subnet mask
A 1 – 126*; 255.0.0.0
B 128 – 191; 255.255.0.0
C 192 – 223; 255.255.255.0
D 224 – 239; n/a, Reserved for Multicasting
E 240 – 255; n/a, Experimental; used for research
* Class A addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions.
1st octet:
A 0...  (all other bits total 127, but 0 and 127 are reserved)
B 10...  (128 up to 128+(64-1), all bits below 64 sum to 63)
C 110...  (128+64 up to 128+64+(32-1))
D 1110... etc
E 1111...

Q: ipv4 Private address IP ranges
A: A: 10.0.0.1 - 10.255.255.255 (CIDR /8)
B: 172.16.0.1 - 172.31.255.255  (CIDR /16, "true" CIDR /12)
C: 192.168.0.1 - 192.168.255.255 (CIDR /24, "true" CIDR /16)

Q: Private class B IP range, broadcast, and CIDR
A: 172.16.0.1 - 172.31.255.254, 172.31.255.255 (?), /16 (really /12)

Q: APIPA expansion and definition, and IP
A: Automatic Private Internet Protocol Addressing
(Automatic Private IP Addressing) The Windows function that provides DHCP autoconfiguration addressing. APIPA assigns a class B IP address from 169.254.0.0 to 169.254.255.255 to the client when a DHCP server is either permanently or temporarily unavailable.
169.254 = head shop inhaler   (D SH P = 169, N L R = 254)

Q: Class C private network IP range, broadcast, CIDR
A: 192.168.0.1 - 192.168.255.254; 192.168.255.255; /24 (really /16)

Q: IPv6 loopback address
A: ::1  (0:0:0:0:0:0:0:1)

Q: The two parts of IPv6 address
A: 64-bit (sub-)network prefix, and a 64-bit interface identifier.

Q: Describe each section in the ipv6 address 2001:3200:CADD:1200::/64
A: 2001:32 = registry prefix   (/23)
2001:3200 = ISP prefix (/32)
2001:3200:CADD = site prefix (/48)
2001:3200:CADD:1200 = subnet prefix (/64)
Global: 2000::/3, assigned by the IANA

Q: with ipv6 2001:db8:85a3::8a2e:370:7334/64, what is the "/64" called?
A: The network prefix

Q: Does broadcast exist in ipv6?
A: No

Q: What is the link local address and what does it replace?
A: link local: FE80::/10.  The replacement of the automatic private IP address (APIPA).

Q: if you have a multiple NIC cards, what will the IPv6 link local address be?  What is the extra info called?
A: FE80::%10   ,  %10 is called the zone ID

Q: ipv4 and v6 IPs for RIP, EIGRP, OSPF
A: v4, v6
RIP: 224.0.0.9, FF02::9   (note multicast in ipv6 is FF00::/8)
EIGRP: 224.0.0.10, FF02::a  (a = 10)
OSPF: 224.0.0.5 and .6, FF02::5 and FF02::6
broadcast doesn't exist in ipv6

Q: What is the anycast also known as?  And more detail.
A: anycast: aka "one-to-nearest", normally configured in a router.  Network addressing and routing methodology in which datagrams from a single sender are routed to the topologically nearest node in a group of potential receivers, though it may be sent to several nodes, all identified by the same destination address.
"Nearest" is determined by the appropriate metric of the routing protocol, finds the nearest.  Eg if running RIP, 1 vs 2 hops; EIGRP K metric; OSPF based on cost.

Q: ipv6 address autoconfiguration does what?
A: adds FFFE to the middle of the MAC address of the interface, for use of the interface ID portion of the ipv6 IP address.  Also flips the universal bit (the "2" in the second hex digit).  So, eg
MAC 0060:476E:2502 becomes
(2001:4800:DEAD:800:)260:47FF:FE6E:2502

ipv6: The Neighbor Discovery Protocol (NDP) operates in the Link Layer of the Internet model and is responsible for address autoconfiguration of nodes, discovery of other nodes on the link, determining the link layer addresses of other nodes, duplicate address detection, finding available routers and Domain Name System (DNS) servers, address prefix discovery, and maintaining reachability information about the paths to other active neighbor nodes.
It replaces ipv4 Address Resolution Protocol (ARP) and Internet Control Message Protocol (ICMP) Router Discovery and Router Redirect protocols.
5 packet types:
Router Solicitation, Router Advertisement, Neighbor Solicitation, Neighbor Advertisement, Redirect

Q: What are the 5 packet types in the ipv6 NDP?
A: Router Solicitation
Router Advertisement
Neighbor Solicitation
Neighbor Advertisement
Redirect

Q: What is ARP, what does it stand for, and what is it used for?
A: Address Resolution Protocol.  ARP is used for converting a network address (e.g. an IPv4 address) to a physical address like an Ethernet address (also named a MAC address)

Q: What is ICMP, what is it used for?
A: The Internet Control Message Protocol (ICMP) is used by network devices, like routers:
- send error messages (e.g. indicating that a requested service is not available or that a host or router could not be reached).
- can also be used to relay query messages.
Not typically used to exchange data between systems, nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools like ping and traceroute).

Q: What command must you type to enable routing in ipv6?
A: R1(config)#ipv6 unicast-routing

Q: What are the 3 transition mechanisms from ipv4 to v6, and what do they do?
A: dual stack: run 2 routing protocols at the same time
6-to-4 tunnelling: encapsulates IPv6 packets in IPv4 packets for delivery across an IPv4 infrastructure.
NAT-PT (Network Address Translation (NAT)-Port Translation (PT) ): translates addresses both ways.  Not recommended to use this one

Q: List the decimal IP subnet mask values in increasing order (eg subnet mask 255.255.128.0 - what are the other valid values?)
A: 128 = 10000000
192 = 11000000
224 = 11100000
240 = 11110000
248 = 11111000
252 = 11111100
254 = 11111110
255 = 11111111

When using RIPv2 and EIGRP for cert exam, you will advertise networks using the classful boundaries.  When using OSPF, advertise networks with wildcards .
Extra: router ospf 1
network 192.168.1.0 0.0.0.255 area 0
network 10.1.1.4 0.0.0.3 area 0 -> contains hosts 10.1.1.5 and .6

Q: ipv6 NDP has DAD - what are the acronyms?
A: Neighbor Discovery Protocol (NDP) - address autoconfiguration of nodes, discovery of other nodes on the link, determining the link layer addresses of other nodes, duplicate address detection, finding available routers and Domain Name System (DNS) servers, address prefix discovery, and maintaining reachability information about the paths to other active neighbor nodes
Duplicate address detection (DAD): nodes can check whether an address is already in use.

Q: What are 3 ways to connect to a router?
A: Console (blue cable)
Auxiliary (modem)
VTY line (telnet or ssh from computer)

Connecting to a router with console:
Use a baby blue console cable from computer port RS 232 to router console, on the computer click on terminal, check settings bits per second 9600, flow control none.  If you don't have a console cable you can use a rolled cable (568B mirrored) with a terminal adapter.

Q: What are the four types of memory of a router you need to know?
A: ROM, RAM, NVRAM, FLASH

Q: What things are stored in router ROM?
A: POST (Power On Self Test), bootstrap, mini-ios, ROMMON
Mini-ios is troubleshooting, can boot to this if needed.
ROMMON = ROM monitor mode.  Prompt "ROMMON 1>" means that your ios is missing or corrupted.

Q: Describe roughly router startup sequence
A: Post->bootstrap->IOS->Config->Run (Pretty Boys Invent Cars for Racing)
From Wallace:
1. POST (power on self test)
2. Execute bootstrap code
3. Locate Cisco IOS software (check config register to determine where to load from)
4. Load Cisco IOS software
5. Locate config (NVRAM, or TFTP)
6. Load config
7. Execute config

Q: What is held in router RAM?
A: RAM: random access mem - volatile.
Has run (running config), arp cache, routing table, packet buffers.

Q: What router command writes the running config to NVRAM?
A: Use "copy run start" or "write" to write the running config to NVRAM.

Q: What does router NVRAM hold?
A: NVRAM: hard drive: start config (always "copy run start" to save it)

Q: What is in router flash memory?
A: FLASH: ios; ios is compressed in hardward but is decompressed when it's loaded.  Each flash card is series-specific.

Q: Router booting: when it finds the IOS in flash, what does it do next?
A: looks at registry settings to see if it needs to load a config
2102 = look at NVRAM and tell me if configs are there, and if there load them (into RAM)
2142 = ignore configs

Q: Layers of TCP/IP model, and their mapping to OSI
A: Application, Transport, Internet, Network Access: All Teens Imagine Naked Adults
transport or host-to-host layer
network or link layer

When configuring a router, and you first log in, the initial prompt ">" shows that you're in user mode.  To "unlock" the router and get into privileged mode, type "enable".  Then to configure, type "configure terminal" or "config t", which gets you to global configuration mode.

ipv6 NDP packet types:
Router Solicitation: used by hosts to locate routers on an attached link.
Router Advertisement: Routers periodically advertise their presence together with various link and Internet parameters, or in response to a Router Solicitation message.
Neighbor Solicitation: used by nodes to determine the link layer address of a neighbor, or to verify that a neighbor is still reachable via a cached link layer address.
Neighbor Advertisement:  used by nodes to respond to a Neighbor Solicitation message.
Redirect: Routers may inform hosts of a better first hop router for a destination.

Configure router: Security
#enable password cisco => sets the password - note that the password here is plaintext!
#enable secret student => sets the (override) encrypted password
These are both called "privilege-mode passwords"
#service password-encryption => encrypts all plain-text passwords
The "enable secret xxx":
- always overrides the "enable password"
- has higher encryption than "service password-encryption"
Create user:
#username ldiaz privilege 15 password 0 pwd => create users with admin level (1 is low, 15 is high)
Question: for the above, is the password encrypted? Ans: password 0 => it's plain text, but the previous "service password-encryption" encrypts it anyway.

Configure router: Lines
There are three types of lines: auxiliary, console, and virtual terminal.
#line console 0 => configuring console
#line vty 0 15 => to configure all the virt term lines (assuming 15 lines, use "line vty 0 ?" to find number of lines)
#line aux 0 => to configure aux
#password cisco => sets the password for line configuration!
#login => tells the router to look under the console line configuration for the password. If you do not use this command, you will not be prompted for a password when you connect to the router’s console port.
#login local => must use configured username and password
#exec-timeout 0 0 => sets the timeout, 0 mins and 0 seconds; no timeout in this case
#logging synchronous => information doesn't interrupt your typing

Q: Collision domain:
when does it happen, what happens?
A: a part of a network where packet collisions can occur. A collision occurs when two devices send a packet at the same time on the shared network segment. The packets collide and both devices must send the packets again, which reduces network efficiency. Collisions are often in a hub environment, because each port on a hub is in the same collision domain. By contrast, each port on a bridge, a switch or a router is in a separate collision domain.

Q: Broadcast domain: what is it?  hub, switch, and router considerations
A: A broadcast domain is a domain in which a broadcast is forwarded. A broadcast domain contains all devices that can reach each other at the data link layer (OSI layer 2) by using broadcast.
All ports on a hub or a switch are by default in the same broadcast domain. All ports on a router are in the different broadcast domains and routers don't forward broadcasts from one broadcast domain to another.

Q: [...] - the speed of the connection you have to the other router.  Sets the Serial interface clockrate in BPS (bits per second).  It is only applicable on a [...].
In most instances the service provider sets this speed, you need just match it.  This has nothing to do with bandwidth.  Clockrate merely allows the routers or DCE equipment to communicate properly.
A: "clock rate"; serial interface

DCE = Data Circuit-terminating Equipment.
DTE = Data Terminal Equipment
Clocking is provided by the DCE, not by the DTE.
if you want to know which side is your DCE side (the interface side that you need to add the clock rate), run the command show controllers <name> ... the cable will be identified as DCE or DTE.

Q: If you don't set the clock rate on a router, what kind of issue will you have?
A: Layer 2 issue (status up, protocol down)

Q: show ip int brief statuses:
"status down, protocol down" = [...].
"status = up, protocol = down" = [...].
"administratively down" = you need to [...]
A: a layer 1 issue, physical cable or interface, not attached; physically fine, but a logical issue - a layer 2 issue (encapsulation mismatch, translation, clocking, CRCs); "no shut"

Show commands:
"show run" - what's current config'd.  Looks in RAM
"show start" - looks at NVRAM, which will be loaded at boot.
"show ip int brief" - check the ips.
"show protocols" - shows IP *and* mask
"show flash" - shows ios name
"show version" - ios, feature set, copyright, RAM, NVRAM, flash, configuration register.
"show int f0/0" - hardware info, IP, protocol info
"show ip int s0/0/0" - ip info, access lists, etc.

Q: A DHCP server [...] IP addresses.  It doesn't [...] them.
A: leases; assign

Q: What is DHCP?
A: Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway.

Q: Suppose you had a router with 2 broadcast domains, a host on int f0/0, and a DHCP server at ip 192.168.1.101/24 on int f0/1.  What command is needed to allow that host to reach the DHCP server?
A: #config t
#int f0/0
#ip helper-address 192.168.1.101
#exit

Collision domains:
All ports on a hub are in the same collision domain.
Each port on a bridge, a switch or a router is in a separate collision domain.
Broadcast domains:
All ports on a hub or a switch are by default in the same broadcast domain.
All ports on a router are in different broadcast domains.

Q: How do you add a static name-to-address mapping on a router?
A: #config t
#ip host <name> <ip address> <other ips>

Q: If you're on a router, how can you get information about the machines connected to that router?
A: #show cdp neighbors
#show cdp neighbors detail
CDP = "cisco discovery protocol"

Q: What are the fields returned by "show cdp neighbors" or "show cdp neighbors detail"
Fields returned:
Device ID
Local Intrfce
Holdtme
Capability
Platform
Port ID
A: Fields returned:
Device ID - the device
Local Intrfce - the local port used to connect to the other device
Holdtme - how long info will be held
Capability - what the other device is
Platform - the platform of the other device
Port ID - the port of the other device
detail:
Interface: <local>, Port ID (outgoing port): <remote port>
IP address: the IP of the remote thing

Q: How do you turn CDP on/off for a router (two levels!)?
A: Globally:
#config t
#cdp run
#no cdp run
Per interface
#config t
#int f0/0
#cdp enable
#no cdp enable

Q: How can you get a configured router to restart with a blank running config, and then how do you get it to have the startup config?
A: To skip loading NVRAM:
#config t
#config-register 0x2142
#exit
#show version => shows that it will start with 0x2142
#copy run start
#reload
on load, starts with nothing!
can do "#config t"
#copy start run
#config-register 0x2102    ! YOU MUST DO THIS
#exit
#reload
2142 = NOT RUN (NT RN = 2142)
You may need to "no shut" the interfaces when the router reloads!

Q: How do you get into ROMMON?
A: turn off and back on, then Ctrl+C during boot
"rommon 1 >" prompt

Q: How would you reset a forgotten router password? (hint: registry config)
A: Get into rommon (turn router off and back on, then Ctrl+C during boot)
rommon 1 >confreg 0x2142
rommon 1 >reset
... reloads, and you're in an unconfigured router
#en
#copy start run
check the interfaces, they may be down ... "no shut" if needed
... change password, copy-run-start ...
#enable secret thenewpassword
#copy run start
#config-register 0x2102    (change the registry back!)
#copy run start

Q: What is the basic difference between static and dynamic routing?
A: Static routing: process of manually entering routes into a device's routing table.  These manually configured routes don't change after they are configured (unless a human changes them) they are called 'static' routes.  Static routing does not handle failures in external networks well because any route that is configured manually must be updated or reconfigured manually to fix or repair any lost connectivity.
Dynamic routing protocols are supported by software applications running on the routing device (the router) which dynamically learn network destinations and how to get to them and also advertise those destinations to other routers.  Router selects one or more 'best' routes for each network destination the router knows or has learned.  This gives dynamic routing protocols the ability to adapt to logical network topology changes, equipment failures or network outages 'on the fly'.

Q: What should you exclude from a DHCP pool?
A: exclude things with static IP addresses: DNS server, file server, print server, domain controller.

Q: Configure a router to be a basic DHCP server.
A: #en
#config t
(config)#ip dhcp excluded-address 192.168.1.1 192.168.1.20  (NOTE: done in global config mode)
(config)#ip dhcp pool laz
(dhcp-config)#default-router 192.168.1.254  (sets the gateway)
(dhcp-config)#network 192.168.1.0 255.255.255.0  (sets network so it can assign addresses)
(dhcp-config)#dns-server 192.168.1.254
#exit
#copy run start
Always put in these two things: the network, the gateway
N - DR - DS (network, default router, dns server)

Q: Do: config console and vty lines 0-15: add password, set timeout, etc.
A: # line con 0
# login local
# exec-timeout 0 0
# logging synchronous
# line vty 0 15
# login local
# exec-timeout 0 0
# logging synchronous
# transport input all   ## allow which protocols for this line?
# exit
Note: "login local" means use the prev. configured "username x password y" users to log in.  Could also do "login / password x", but that would only work for Telnet.  SSH requires "login local" (at least, I think so), and it also requires "crypto key generate rsa (which in turn needs a hostname and ip domain-name)".

Q: Commands to configure router basics
A: hostname R2
banner motd $hello there$
no ip domain-lookup    (this is better!)
ip domain-name cisco.com
ip name-server 192.168.1.2

Q: Commands to configure router security
A: enable password cisco
enable secret student
service password-encryption
username ldiaz privilege 15 password 0 cisco
crypto key generate rsa
512
And secure the lines

Q: Commands to configure router interface
A: # int f0/0
# ip address 192.168.2.254 255.255.255.0  (network, mask)
# description connection to LAN
# no shut   (bring it up)
# int s0/0/1
# ip address 10.1.1.6 255.255.255.252
# no shut
# exit

Q: TCP/IP Application layer function
A: Defines TCP/IP application protocols and how host programs interface with transport layer services to use the network.  encrypt/de, starts/maintains/ends sessions.

Q: TCP/IP Transport layer function
A: services such as connection-oriented data stream support, reliability, flow control, and multiplexing.
RFM reliability flowcontrol multiplexing

Q: TCP/IP Internet layer function
A: Packages data into IP datagrams, which contain source and destination address information that is used to forward the datagrams between hosts and across networks. Performs routing of IP datagrams.

Q: TCP/IP Network Access layer function
A: Specifies details of how data is physically sent through the network, including how bits are electrically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper wire.

Q: TCP/IP Application layer protocols
A: HTTP, Telnet, FTP, TFTP, SNMP, DNS, SMTP, X Windows, SSH, other application protocols

Q: TCP/IP Transport layer protocols
A: TCP, UDP, RTP

Q: TCP/IP Internet layer protocols
A: IP, ICMP, ARP, RARP

Q: TCP/IP Network Access layer protocols
A: Ethernet, Token Ring, FDDI, X.25, Frame Relay, RS-232, v.35

Q: What layers of data do switches access?  What layers do routers access?
A: Switches use layer 2 data (Data Link layer) to forward frames but they can't access layer 3 data.
Routers use layer 2 and 3 data (Data Link and Network).  They have read-only access to layer 3 data (Network), but can read and write layer 2 data (Data Link).

Q: Static vs dynamic routing - major points
A: Static:
- easy on the router, hard on the human (have to enter all of it).  Best for small networks.
Dynamic:
- hard on the router, easy on you.  Handles redundancy.  Algorithms calc paths.  Updates are sent/triggered, bandwidth.  Need to choose the routing protocol.
Need to analyze the network to determine which way to go - static v dynamic (and which protocol if the latter).

Q: Configure a serial router interface
A: R2(config-if)#int s0/0/1
R2(config-if)#description to R3
R2(config-if)#clock rate 4000000    <<<<< (on DCE end!)
R2(config-if)#ip address 10.1.1.5 255.255.255.252
R2(config-if)#no shut

Q: Add a static routes to a router so that:
- host 192.168.3.1/24 on the network segment on interface s0/0/1 can be reached.
- any unknown networks get sent to s0/0/2
A: #ip route <network> <mask> <interface>
R2#config t
R2(config)#ip route 192.168.3.0 255.255.255.0 s0/0/1
R2(config)#ip route 0.0.0.0 0.0.0.0 s0/0/2
R2(config)#exit
for point-to-point networks, cisco recommends exit interfaces for static routes (that is "s/0/0/0")

Q: What is a default route, and what is it also known as?
A: default route is so that the router, when it receives a destination network that it doesn't have an entry for in the routing table, it doesn't drop it.
AKA the "gateway of last resort"

Q: How do you see the configured static routes on a router?
A: R1#show ip route
Codes: C - connected, S - static, ...
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
     10.0.0.0/30 is subnetted, 1 subnets
C       10.1.1.0 is directly connected, Serial0/0/0
C    192.168.1.0/24 is directly connected, FastEthernet0/0
S*   0.0.0.0/0 is directly connected, Serial0/0/0
Note connected, static route, and default route!

Q: What is the simplest kind of route that could be added to this router to allow for traffic, and what are the commands?
A: A default route - this is an "end router"
R3#config t
R3(config)#ip route 0.0.0.0 0.0.0.0 s0/0/0
R3(config)#exit

Q: For routing, what is the "administrative distance"?
A: "administrative distance" - the believability of a route.  Lower number = more believable.  Determines if a route makes it into the routing table.
Directly connected = 0; routing protocols have different numbers
The administrative distance (AD) of a static route is 1 by default (can be overridden), regardless of whether it is pointing to an interface or an IP address.

Q: Suppose you're using dynamic routing, but you want some backup in case it fails.  What can you do?
A: Config static routing with a higher administrative distance than the dynamic routing, so it's there as a fallback.
R2(config)#ip route 192.168.5.0 255.255.255.0 s0/0/0 150
150 is a higher distance than the dynamic routing protocol

Q: What are distance vector routing protocol disadvantages?
A: Distance vector routing protocol disadvantage: summarizes automatically (only sees the classful boundary). eg, it wouldn't understand a class A /24 network.
YOU MUST USE "no auto-summary" - sends the true subnet mask out; also allows you to have discontiguous networks

Q: Describe some basics about RIPv2: what is it, limitations
A: RIPv2
- distance vector routing protocol
- only cares about distance (hop count), limited to 15 hops
- every 30 seconds you send the entire routing table out on the updates (bandwidth issue)
- Distance vector:
- summarizes automatically so you MUST TYPE "no auto-summary" (or it summarizes to the classful boundary)

Q: Describe some basics about EIGRP: what is it, limitations
A: - Cisco-specific, can only be used on Cisco routers.
- Advanced distance vector routing protocol
- has traits from OSPF and traits from distance vector
- Distance vector:
- summarizes automatically so you MUST TYPE "no auto-summary" (or it summarizes to the classful boundary)
- hop count limitation of 255 routers
- Link state advantage:
- sends all updates first time and only sends updates.  EIGRP is based on autonomous systems.  Creates a topology table.

Q: Describe some basics about OSPF: what is it, limitations
A: - a whopper routing protocol, for huge networks
- Link state (LS) routing protocol
- No limitation, based on areas (can have >4.2 billion areas, can be huge)
- During test: OSPF for single-area is all need to be concerned with
- Very processor intensive, does a lot of calcs (OSPF = Open Shortest Path First), so CPU intensive.

Q: Do: A router has 10.1.1.4/30 reachable via s0/0/0.  Config RIPv2, and a static route as a fallback.
A: # config t
# ip route 10.1.1.4 255.255.255.252 s0/0/0 150
# router rip
# version 2
# no auto-summary
# network 10.0.0.0
! note the 150 is the admin distance, required!

Some facts about RIP:
type of routing protocol: distance vector (distance = hops)
max hop count: 15, 16 is unreachable
algorithm: bellman-ford
administrative distance: 120

Q: What are the RIP timers?
A: update timer: 30 s.  RIP sends out the entire routing table every 30 s
holdown timer (hold down): 180 s - it will hold the update information for 180 s
invalid timer: if I don't receive an update  at the end of 30 s, starts ticking and if haven't received an update, the route is invalid (still in routing table)
flush timer: 240 s - after the invalid timer expires, this timer starts; after this expires, the route is removed
Note the holdown and invalid have to be the same

Q: Why would you increase the RIP timers?
A: - save bandwidth
- prevent up-and-down interface - flapping interface - increase the timers to have it hold information for longer

Q: What is Split Horizon, and what does it accomplish?
A: Split Horizon is a technique used by distance vector routing protocols for avoiding routing loops.  A router will not advertise a route out of an interface on which it learned that route.
Since R3 learned about 172.16.1.0/24 from interface f0/0, it will not advertise that network out of int f0/0 (it could advertise it out of other interfaces).  If it did, then R2 would update its routing table, and say that 172.16.1.0/24 was out of its f0/1 interface, which it's not!

Q: What is Route Poisoning, and Poison Reverse?
A: Assigning an infinite metric to a route to tell everyone it's unreachable.  Eg for RIP, with max hop count 15, assign it a max hop count of 16.  "Poisons the route"
Poison Reverse (from https://learningnetwork.cisco.com/thread/7712)
When a router receives a route poisoning, it sends an update back to the router from which it received the route poisoning.  This is called poison reverse.  This is to ensure that all routers on a segment have received the poisoned route information.

Q: Configure a router so that it accepts RIP v2 updates on interface f0/0, but doesn't broadcast.
A: #router rip
#version 2
#no auto-summary
#network 10.0.0.0   !see note below
#passive-interface f0/0
Note: If an interface belongs to a network defined by this command, the interface will participate in the RIP routing process. If an interface does not belong to a network defined by this command, it will not send or receive RIP updates.
ref http://www.cisco.com/c/en/us/td/docs/security/
asa/asa84/configuration/guide/asa_84_cli_config/route_rip.html

Q: A router is connected to a server with IP 192.168.1.1/24 on interface s0/0/0.  You want that to be the default route for that router, and all other routers should reach that server as well, on a RIPv2 router network.  Set that up.
A: #config t
#ip route 0.0.0.0 0.0.0.0 s0/0/0
#router rip
#version 2
#default-information originate    !propagates
#no default-information originate   !turn it off

Q: What address does RIP send info on?
A: RIP's (multicast) address: 224.0.0.9; OR ff02::9

Q: How can you see what's going on in RIP under the hood?
A: >enable
#debug ip rip
#no debug ip rip

Q: Configure RIPv2 on a router, include network 10.1.1.4/30 and 192.168.1.0/24 in the updates
A: # config t
# router rip
# version 2    !don't use version 1
# no auto-summary
# network 10.0.0.0    !classful boundaries
# network 192.168.1.0
3 summary steps: Enabling RIP routing protocol on the router, Specifying the RIP version to run, Configuring the network addresses to be included in routing updates or specifying the interfaces to participate in routing updates.

Q: What command must you never forget with RIPv2 and EIGRP?
A: no auto-summary

Q: "sh ip route" returns the following line, what does it mean?
"R 192.168.1.0/24 [120/1] via 10.1.15, 00:00:05, Serial0/0/0"
A: We learned about 192.168.1.0 network from RIP, AD dist 120, 1 hop, via 10.1.1.5 network, on serial s0/0/0, info is 5 s old

Q: Set the IPv6 for a router interface
A: # int s0/0/1
# ipv6 address 2001:3200:face:1300::2/56   !! note /56
Don't forget #ipv6 unicast-routing

Q: Your router has int f0/0 with ipv6 2000:3200:FACE:1000::1/56.  Set up RIPng (ipv6 RIP).
A: R1#config t
R1(config)#ipv6 router rip process1   !auto-added if you rip 1 an interface
R1(config-rtr)#int f0/0
R1(config-if)#ipv6 rip process1 enable
Don't forget #ipv6 unicast-routing

Q: What is IGP?
A: An interior gateway protocol (IGP) is a type of protocol used for exchanging routing information between gateways (commonly routers) within an autonomous system (for example, a system of corporate local area networks).
This is how EIGRP and OSPF exchange routing table info.

Q: EIGRP: What is the autonomous system number (AS)?
A: EIGRP based on autonomous systems - autonomous system number - AS.  Number from 1 - 65535, can have this many aut. systems.  For CCNA, only need single AS.  The autonomous system (AS) will be based on single AS number, so the AS number *must be* the same on all the routers.

EIGRP facts:
Acronym: Enhanced Interior Gateway Routing Protocol
Type of protocol: hybrid protocol, also called advanced DV routing protocol (both link state and distance vector)
Max hop count: 255, but set by default to 100
Supported by all routers? Only supported by Cisco routers (both ipv4 and 6).
Algorithm: Diffusing Update Algorithm (DUAL)
Administrative distance: 90

Q: What factors does EIGRP use to calculate the best route?
A: Bandwidth (kilobytes per second, on the weakest link)
Delay (10s of microseconds)
Reliability (value ranging from 1 to 255; 255 being the most reliable)
Load (value ranging from 1 to 255; 255 being saturated)
MTU (not really used)
Big Dogs Really Like Me.
Defaults are Bandwidth and Delay.

Q: In EIGRP, what are the criteria for adjacency?
A: 3 criteria:
- same AS number
- identical K-values
- Hello (in reality, Hello not really heeded)

Q: What are the different acronyms in EIGRP (eg, successor, etc)?
A: AD: advertised/reported distance.  Distance from our EIGRP neighbor to a network.
FD: feasible distance.  Distance from me to another network via a neighbor.  Advertised Distance + metric to the neighbor reporting the route.
SR: successor route.  Lowest feasible distance, is what is in the routing table
FS: feasible successor (backup route, in topology, can have up to 8 FS)
For all the above, distance really means "metric"

Q: What tables does EIGRP create?
A: Neighbor table: info about neighbors it found.
Topology table: has all known routes.
Routing table: has best routes to destinations based on lowest metric.
TRAIN - Topology, Routing, Neighbor

Q: What command do you use to see a router interface f0/0's bandwidth, delay, reliability, MTU, load?
A: R2#show int f0/0
FastEthernet0/0 is up, line protocol is up (connected)
  Hardware is Lance, address is 0030.a38b.e901 (bia 0030.a38b.e901)
  Internet address is 10.1.1.14/30
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255

Q: What command do you use to look at a router's EIGRP topology table?
A: # sh ip eigrp topology
R2#show ip eigrp topology
IP-EIGRP Topology Table for AS 1
...
Codes: P - Passive, A - Active, U - Update, Q - Query,...
...
P 10.1.1.4/30, 1 successors, FD is 2172416
         via 10.1.1.13 (2172416/2169856), FastEthernet0/0

Q: Configure a router to use EIGRP for ipv4, network 10.1.1.4/32 and 192.168.1.0/24.
A: #config t
#router eigrp 1
#no auto-summary
#network 10.0.0.0    !classful boundary
#network 192.168.1.0
Then do the other routers, with the same autonomous system.

Q: What determines if a route makes it into the routing table?
A: The administrative distance (and nothing else!)

Q: "show ip route" returns the following line, what does it mean?
"D 10.1.1.4 [90/2681856] via 10.1.1.9, 00:00:05, Serial0/0/0"
A: EIGRP ("D" = Dual), with admin distance 90, and the metric.

Q: Your router has s0/0/1 with IP 2000:1:1::1/56 and f0/0 with IP 2000:1:1::2/56.  Configure eigrp for ipv6.
A: #config t
#ipv6 router eigrp 100
#router-id 1.1.1.1   !unique for each router
#no shutdown   !need to activate it
#int s0/0/1
#ipv6 eigrp 100
#int f0/0
#ipv6 eigrp 100

Q: How do you see the ipv6 routes in a router?
A: show ipv6 route

Q: How do you see the neighbors for a router in EIGRP?
A: show ip eigrp neighbors

Q: "show IP EIGRP topology" returns some rows starting with P, some with A - what does that mean?
A: P = passive, fully converged, A = active, still looking, not fully converged

Q: If you're configuring EIGRP, and your router has s0/0/0 going out to the internet, how should you configure the router?
A: R1(config)#router eigrp 1
R1(config-router)#passive-interface serial 0

Q: During exam/simulation, what should you do to check basic communication?
A: Sit on one router, and ping all of the others.

Q: What are the three things to ensure when setting up EIGRP, and 2 extra when checking?
A: - in the same autonomous system
- advertise the classful boundaries of the networks that you are connected to
- "no auto-summary"
- same K values (default)
- also check "no passive-interface xxxx" if needed

Q: How do you check the EIGRP K values for a router?
A: R2#show ip protocols
Routing Protocol is "eigrp  1 "
...
  EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
Change them with:
R1(config)#router eigrp 20
R1(config-router)#metric weights 0 1 0 1 0 0   !first param must be 0

Q: How would you change a router's EIGRP metrics to match the below? (note: AS=20)
EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
A: R1#config t
R1(config)#router eigrp 20
R1(config-router)#metric weights 0 1 0 1 0 0
(note: there are five K values, so why 6 numbers? The first number listed is type of service (ToS), so always just set that to 0, which means you must type in six numbers as shown in my configuration example.)
ref Lammle pg 824

OSPF facts
Type of Protocol: Link state
Classless support: Yes
VLSM support: Yes
Auto-summarization: No
Manual summarization: Yes
Noncontiguous support: Yes
Route propagation: Multicast on change
Path metric: Bandwidth
Hop count limit: None
Convergence: Fast
Peer Authentication: Yes
Hierarchical network requirement: Yes (Using multiple areas)
Updates: Event Triggered
Algorithm: Dijkstra

Q: OSPF Terminology definition: Link
A: A network or router interface assigned to a given network and added to the OSPF process.

Q: OSPF Terminology definition: Neighbor
A: two or more routers that have an interface on a common network. OSPF neighbors MUST have the following in common in order to establish neighbor relationship.
- Area ID
- Subnetmask
- Hello and Dead intervals
- Authentication password (Optional, but if it’s present, they must be the same)
i think MTU

Q: OSPF Terminology definition: Adjacency
A: Routers that are neighbors, and also that exchange LSU and DBD (database descriptor) packets.

Q: OSPF Terminology definition: Designated router
A: A DR is elected whenever multiple OSPF routers are connected to the same broadcast network to minimize the number of adjacencies. Designated router is elected based on certain criteria, priority levels (0-255), highest priority becoming the DR, if equal priority, uses the highest router ID (ID, then highest loopback, then highest IP)

Q: OSPF Terminology definition: Backup designated router
A: BDR is a hot standby for the DR in the broadcast or multi-access network. BDR’s receive routing updates, but do not send out LSA updates.

Q: OSPF Terminology definition: Hello protocol
A: An OSPF hello protocol provides dynamic neighbor discovery and maintain neighbor relationships (confirm reachability).
Hello packets use the multicast address 224.0.0.5 (in multi-access network, will use 224.0.0.5 and 224.0.0.6 - 6 is for the DR and the BDR)

Q: OSPF Terminology definition: Neighborship database
A: Is a list of all OSPF routers that have seen Hello packets. Also the RID and state are maintained in this database.

Q: OSPF Terminology definition: Topological database
A: This database contains information from all of the LSAs (Link State Advertisement) that have been received for an area. The topology database is used as an input for the Dijkstra algorithm to compute the shortest path (SPF) to all networks

Q: OSPF Terminology definition: Link State Advertisements
A: Link state and routing information, used to construct a Link State Database. Only routers that have established adjacencies will exchange LSAs.
LSAs are contained inside of LSUs (Link State Updates)

Q: OSPF Terminology definition: OSPF areas
A: A grouping of contiguous networks and routers. Routers with the same area ID are in the same area.

Q: OSPF Terminology definition: Broadcast (multi-access)
A: BMA networks allow multiple devices to connect to or access the same network.  e.g., Ethernet.

Q: OSPF Terminology definition: Nonbroadcast multi-access
A: NBMA networks allow for multi-access without the broadcast ability.  e.g., example: Frame-relay.

Q: OSPF Terminology definition: Point-to-Point
A: In this context PPP refers to a type of network topology made up of direct connections between routers, which will create a single communication pathway.

Q: OSPF Terminology definition: Point-to-Multipoint
A: This network type is made up of a series of routers, connected from a single routers interface to multiple destination routers. All routers belonging to the same point-to-multipoint topology are in the same network.

Q: Do: add loopback 1.1.1.1/32 interface to a router.
A: # config t
# int loopback 0  !or some number
# ip address 1.1.1.1 255.255.255.0
# show ip int brief
- fake interface that a router uses to communicate with itself, helps us test and admin
- can assign IP address to the whole router, not to any particular interface

Q: What is a point-to-point network?
A: Point-to-point refers to a type of network topology made up of a direct connection between two routers that provides a single communication path. The point-to- point connection can be physical—for example, a serial cable that directly connects two routers—or logical, where two routers thousands of miles apart are connected by a circuit in a Frame Relay network.

Q: Configure OSPF on a router connected to 192.168.1.0/24 and 10.1.1.4/30.
A: # config t
# router ospf 1
# network 192.168.1.0 0.0.0.255 area 0  !using wildcard masking
# network 10.1.1.4 0.0.0.3 area 0  !must be in the same area
# network 172.31.1.0 0.0.0.255 area 0  !must do the loopback

Q: What is the ospf process ID, and what range must it be in?
A: # router ospf <process ID>
1 - 65535 - must be in this range.  All it does, it keeps track of the link state database, and it's local.

Q: What are the OSPF adjacency ("becoming neighbors") state changes?
A: down state
init state: Hello Sent from R1 to R2 (224.0.0.5 multicast)
2-way state: Hello from R2 to R1, which includes both R2 and R1's router ID.  Go into 2-way when the Hello message contains our router ID.
Note R2 is still in init state, until it receives another Hello containing itself from R1.
When both are in 2-way state, DR/BDR election happens, if needed.
exstart state: routers choose master-slave relationship (primary/secondary)
exchange state: routers exchange database descriptor (DBD) packets - contains a list of all of the known LSAs.
loading state: if need info, send LSRs to get LSUs containing LSAs
full state: both routers know about all the routes
NOW OSPF CAN BEGIN SPF CALCULATIONS
ref http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13685-13.html

Q: "show ip route" returned the following - what does it mean?
"O 10.1.1.4 [110/128] via 10.1.19, 00:00:03, Serial0/1/0"
A: OSPF line, Admin distance = 110, cost = 128 (calc'd by algorithm)

Q: How can you see the ospf router id?
A: R1#show ip ospf interface f0/0
...
  Process ID 1, Router ID 172.31.1.1, ...

Q: How is the ospf router ID chosen?
A: The OSPF router-id will be, in order:
1. The one configured by the router-id command, if available and configured
2. The highest IP loopback interface when OSPF starts, if a loopback exists
3. The highest IP on a non-loopback interface.
https://learningnetwork.cisco.com/thread/16047

Q: How do you see the Designated Router, BDR in a router's ospf area?
A: "show ip ospf int f0/0" - shows a bunch of data, such as priority, router id, cost, DR, BDR

Q: If you type "show ip ospf int <xxx>" and see "Priority 0", what will you also see?
A: No designated router (DR), no backup designated router (BDR).  The zero priority doesn't run the election.

Q: What things must be the same for OSPF routers to become neighbors?
A: - Area ID
- Subnet mask
- Hello and Dead intervals
- MTU size (OSPF v2)
- Authentication password (Optional, but if it’s present, they must be the same)
- matching stub flags

Q: What type of network will result in OSPF having an election for a DR and BDR?
A: Broadcast-type network (e.g., Ethernet)

Q: In OSPF, what is the first thing checked when a DR/BDR election is held?
A: The OSPF priority number

Q: In OSPF, what area is the backbone area?
A: Area 0

Q: How do you see the state of a router's connected routers for OSPF?
A: Router#show ip ospf neighbor
eg returns:
Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.3       1   FULL/DR         00:00:30    192.168.1.3     FastEthernet0/0
192.168.1.2       1   FULL/BDR        00:00:34    192.168.1.2     FastEthernet0/0
192.168.1.1       1   2WAY/DROTHER    00:00:36    192.168.1.1     FastEthernet0/0

Q: How do you read the following output?
Router#show ip ospf neighbor
Neighbor ID     Pri   State           Dead Time   Address         Interface
192.168.1.3       1   FULL/DR         00:00:30    192.168.1.3     FastEthernet0/0
192.168.1.2       1   FULL/BDR        00:00:34    192.168.1.2     FastEthernet0/0
192.168.1.1       1   2WAY/DROTHER    00:00:36    192.168.1.1     FastEthernet0/0
A: These are all neighbors - .3 is the Designated Router, .2 is the Backup DR, and .1 is in "2way" state (it's a "DROTHER").

Q: How do you get the OSPF state of a router?
A: Router#show ip ospf int f0/0
FastEthernet0/0 is up, line protocol is up
  Internet address is 192.168.1.4/24, Area 0
  Process ID 1, Router ID 192.168.1.4, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State DROTHER, Priority 1

Q: How do you "reset" ospf to force a reload?
A: "clear ip ospf process"

Q: Do: Add a loopback address 1.1.1.1/32 to a router running OSPF (assume req'd OSPF data)
A: #config t
#int loopback 0
#ip address 1.1.1.1 255.255.255.255
#exit
#router ospf 1   !process id
#network 1.1.1.1 0.0.0.0 area 0
#exit
#exit
#copy run start

Q: Do: ensure that a router is selected as the Designated Router in its OSPF area.
A: Set the priority:
Router#config t
Router(config)#int f0/0
Router(config-if)#ip ospf priority 255  ![0-255], highest wins

Q: In OSPF, area 0 is the backbone area.  Everyone needs to connect to area 0 directly or indirectly.  What is the router that connects you to area 0 called?
A: An area border router.

Q: How do you see the MAC addresses a switch knows about?
A: >enable
#show mac-address-table

Q: When a switch with an empty MAC address table gets an ARP request, what does it do?
A: Floods all other ports with the ARP.

Q: How do you see the vlans in a switch?
A: #show vlan

Q: Does broadcasting still happen on a switch if the switch's MAC address table is full?
A: Yes :-)

Q: When configuring a switch, what must you configure?  And do that.
A: an IP address, and a default gateway
sw(config)#interface vlan 1
sw(config-if)#ip address 192.168.0.9 255.255.255.0
#no shut
sw(config-if)#exit
sw(config)#ip default-gateway 192.168.0.254

Q: What is the golden rule of network design (Laz's golden rule, anyway)
A: 80% of your traffic should be local to your segment!

Q: Do: add IP address 192.168.1.11/24, and gateway 192.168.1.1/24 to a switch
A: # config t
# int vlan 1
# ip add 192.168.1.11 255.255.255.0
# no shut
# exit
# ip default-gateway 192.168.1.1
# exit

Q: Why would you configure an interface in a switch (eg, "int f0/0")?
A: Port security, assign vlans, spanning tree ...

Q: What are the important "show" commands for a switch?
A: show vlan => see how many vlans are on there, and ports assigned
show vtp status => vlan trunking protocol
show mac-address-table
show interface trunk => shows all ports that are trunked
show port-security
show spanning-tree
show run
show start
show cdp neighbor
show cdp neighbor detail

Q: Do: a full basic config of a switch: passwords, create a local user, banner, domain details, set up line for telnet and ssh
A: >en
#config t
#hostname S1
#enable password cisco
#enable secret student
#service password-encryption
#username ldiaz privilege 15 password 0 cisco
#banner motd $ Welcome to S1 $
#no ip domain-lookup
#ip domain-name cisco.com
#ip name-server 192.168.1.254
#line vty 0 15
#password cisco
#login local
#logging synchronous
#exec-timeout 0 0
#transport input all
#line con 0
#password cisco
#login local
#logging synchronous
#exec-timeout 0 0
#int vlan 1
#ip address 192.168.100.253 255.255.255 0
#no shut
#exit
#ip default-gateway 192.168.100.254
 .... copy run start

Q: What port does the BOOTP protocol use?
A: 67 & 68
Shock & Shove in the IP
The Bootstrap Protocol (BOOTP) is a computer networking protocol used in Internet Protocol networks to automatically assign an IP address to network devices from a configuration server.

Q: What port does the DHCP protocol use?
A: 67 & 68
Shock and Shove in the IP, like BOOTP.

Q: What port does the DNS protocol use?
A: 53

Q: What port does the FTP (control port) protocol use?
A: 21
A controlling KNighT (21) with a NoSe (20) for data.

Q: What port does the FTP protocol use?
A: 20 (data port), 21 (control port)

Q: What port does the HTTP protocol use?
A: 80

Q: What port does the IMAP4 protocol use?
A: 143
IMAP4 beats on the DRuM in 4/IMAP4 time.

Q: What port does the LDAP protocol use?
A: 389
LDAP - da real MVP (389)

Q: What port does the NNTP (News) protocol use?
A: 119
Like 911 (on the news) but backwards

Q: What port does the NTP (Time) protocol use?
A: 123
123 ... NTP ... NTP 123, wearing DeNiM.

Q: What port does the POP3 protocol use?
A: 110
POP3's TighTS

Q: What port does the RDP protocol use?
A: TCP port 3389 and UDP port 3389
Miami Fabio :-D

Q: What port does the SMTP protocol use?
A: 25
All mail goes to /dev/NuLL

Q: What port does the SNMP (simple network mgmt protocol) protocol use?
A: 161
DaSHeD network is down, manage it.

Q: What port does the SSH protocol use?
A: 22
SSH, the NuN says.

Q: What port does the SSL/HTTPS protocol use?
A: 443

Q: What port does the TFTP protocol use?
A: 69
SHiP something with TFTP

Q: What port does the Telnet protocol use?
A: 23
NaMe - Telnet.  The Telnet underpants GNoMe.

Q: What protocol uses port 110?
A: POP3
TighTS!

Q: What protocol uses port 119?
A: NNTP (News)
Like 911 (shown on the news), but backwards.

Q: What protocol uses port 123?
A: NTP (Time)

Q: What protocol uses port 143?
A: IMAP4

Q: What protocol uses port 161?
A: SNMP (simple network mgmt protocol)

Q: What protocol uses port 20?
A: FTP (data port)

Q: What protocol uses port 21?
A: FTP (control port)

Q: What protocol uses port 22?
A: SSH

Q: What protocol uses port 23?
A: Telnet
gNoMe of Telnet

Q: What protocol uses port 25?
A: SMTP

Q: What protocol uses port 389?
A: LDAP

Q: What protocol uses port 443?
A: SSL/HTTPS

Q: What protocol uses port 53?
A: DNS

Q: What protocol uses port 67 & 68?
A: BOOTP also used by DHCP

Q: What protocol uses port 69?
A: TFTP

Q: What protocol uses port 80?
A: HTTP

Q: What protocol uses port TCP port 3389 and UDP port 3389?
A: RDP

Q: Do: configure router basics: priv-mode passwords, create user, banner, domain stuff
A: hostname R2
enable password cisco
enable secret student
service password-encryption
username ldiaz privilege 15 password 0 cisco
banner motd $hello there$
ip domain-lookup
ip domain-name cisco.com
ip name-server 192.168.1.2
crypto key generate rsa
512

Q: Do: configure router lines (console and terminal/ssh)
A: line con 0
password cisco
login local
exec-timeout 0 0
logging synchronous
line vty 0 15
password cisco
login local
exec-timeout 0 0
logging synchronous
transport input all   ## allow which protocols for this line?
exit

Q: Do: configure router interfaces f0/0 and s0/0/1
A: int f0/0
ip address 192.168.2.254 255.255.255.0
description connection to LAN
no shut
int s0/0/1
clock rate 4000000  !if DCE
ip address 10.1.1.6 255.255.255.252
no shut

Q: What encapsulation method is used to allow multiple VLANs' traffic to go over a single link?
A: IEEE 802.1Q Encapsulation
To correctly deliver the traffic on a trunk port with several VLANs, the device uses the IEEE 802.1Q encapsulation (tagging) method that uses a tag that is inserted into the frame header. This tag carries information about the specific VLAN to which the frame and packet belong. This method allows packets that are encapsulated for several different VLANs to traverse the same port and maintain traffic separation between the VLANs. The encapsulated VLAN tag also allows the trunk to move traffic end-to-end through the network on the same VLAN.

Q: In ethernet, what is the different between an access port and a trunk port?
A: Ethernet interfaces can be configured either as access ports or a trunk ports, as follows:
An access port can have only one VLAN configured on the interface; it can carry traffic for only one VLAN.
A trunk port can have two or more VLANs configured on the interface; it can carry traffic for several VLANs simultaneously.

Q: Do: On a switch, set port f0/1 to be part of VLAN named "student", and confirm the change
A: #show vlan !get the VLAN number
..., eg 100  student
#conf t
#int f0/1
#switchport mode access
#switchport access vlan 100
(copy run start)
#show vlan  !confirm it

Q: What is special about a native vlan?
A: A native vlan is the untagged vlan on an 802.1q trunked switchport.  The native vlan and management vlan could be the same, but it is better security practice that they aren't.

Q: Do: create vlan named "faculty" on a switch, and add interface f0/3 to it.
A: # config t
# vlan 100
# name faculty !give it a name
# exit
# int f0/3
# switchport mode access
# switchport access vlan 100
exit / copy run start / show vlan !to verify

Q: In the below example, the computers in VLAN 1 can ping each other, but the computers in VLAN 50 can't.  What is a likely explanation and fix for this?
A: Ports needs to be trunked.
On both switches, trunk the ports of the connecting line:
Switch>en
#conf t
#int f0/1
#switchport mode trunk
#switchport trunk allowed vlan 1-99

Q: What is Dynamic Trunking Protocol?
A: A proprietary networking protocol developed by Cisco Systems for the purpose of negotiating trunking on a link between two VLAN-aware switches, and for negotiating the type of trunking encapsulation to be used. It works on Layer 2 of the OSI model.

Q: Do: show what interfaces have been trunked in a router.
A: Switch#show interface trunk
Port        Mode         Encapsulation  Status        Native vlan
Fa0/1       on           802.1q         trunking      1
Port        Vlans allowed on trunk
Fa0/1       1-99
Port        Vlans allowed and active in management domain
Fa0/1       1,50
Port        Vlans in spanning tree forwarding state and not pruned
Fa0/1       1,50

Q: In your switch, int f0/1 currently has vlan 1 as the native vlan.  Do: change the native vlan to vlan 50, and verify it
A: #config t
#int f0/1
#switchport trunk native vlan 50
... copy run start ...
#show int trunk
Port        Mode         Encapsulation  Status        Native vlan
Fa0/1       on           802.1q         trunking      50

Q: What is the purpose of the Spanning Tree Protocol?
A: To avoid switching loops - it blocks ports.  Ports can receive, but won't forward.

Q: How do you see the spanning tree on a switch?
A: show spanning-tree

Q: What is a Root Bridge?
A: A Spanning Tree is an inverted tree. The Root bridge (switch) is a special bridge at the top of the Spanning Tree (inverted tree).

Q: All ports on a Root Bridge (Root Switch) are called what, and are in what state?
A: All the ports in a Root Switch (Root Bridge) are Spanning Tree Designated Ports and will be in Spanning Tree Forwarding State.

Q: How do you see what machine MAC addresses a computer already knows about?
A: Look at the arp cache!
> arp -a

Q: What are the port types/selections that Spanning Tree Protocol makes?
A: Spanning Tree Root Port: best port to reach the Root Switch (Root Bridge)
Designated Port: port in Spanning Tree Forwarding State
Spanning Tree Non-Designated port: port in Spanning Tree Blocking State

Q: What are the STP port states?
A: Blocked: port does not transmit or receive any data, but will listen to BPDUs (Bridge Protocol Data Units)
Listening: The switch listens for BPDUs; listens for and discards frames (not sure if any loops yet).  This port listens to BPDUs to make sure no loops occur on the network before passing data frames.  Doesn't populate MAC address table.
Learning: Listens to BPDUs, learns all paths.  The starts to learn MAC addresses, doesn't forward. Start to transmit its own BPDUs
Forwarding: Learned everything, now forwards traffic
Disabled: receives BPDUs but will not forward them to the switch processor, discards all incoming frames
STP => Big Ladies Love Fried Doughnuts

Q: How many root ports are on non-root bridges, and how are they determined?
A: For non-root bridges there will be only one root port. The root port will be the port with the lowest path cost to the root bridge. The root port will also be set to forwarding state.

Q: How does STP select the root bridge?
A: Looks for lowest Bridge ID.  Bridge ID comprised of two concatenated parts:
- priority number (default 32768 + VLAN number (32768 - MONKEY SHAVE))
- MAC address
Use "show spanning-tree" to see priority and MAC info

Q: What are the steps in the Spanning Tree algorithm?
A: 1. Find your root bridge by looking at bridge IDs (lowest of priority, then lowest MAC)
2. Determine your root ports (finding the lowest path cost to the root bridge ... in case of tie, I'm not sure what the tiebreaker is)
3. Find your designated ports for each link (lowest path cost end is the designated port, then the lower bridge ID - if multiple ports going to the same other router then look at port priority and then port mac ... I think!!)

Q: What are the IEEE SPT link costs?
A: Speed: Cost
10 Mb/s: 100
100 Mb/s: 19
1000 Mb/s: 4
10,000 Mb/s: 2
tosses top R N

Q: Do: make a particular switch to be the Root Bridge for a network.
A: #configure terminal
#spanning-tree vlan 1 priority 0   !can have multiple vlans
(Note: Bridge Priority must be in increments of 4096 ... 2^12 = 4096)
Spanning Tree Protocol Root Bridge election is decided by the lowest Bridge ID, where the Bridge ID = concat. of Priority, VLAN ID, and MAC Address.  Set the priority to a low number!

Q: How does OSPF elect the designated router for an area?
A: 1.  Choose the highest OSPF priority
2.  In case of tie, choose the highest router-id (hardcoded router-id, fallback to highest loopback, fallback to highest interface)
To set the router priority: # conf t
# int f0/0
# ip ospf priority 4    !priority 0 won't be included in election
To set the hardcoded router-id: #conf t
#router ospf 1
#router-id 1.1.1.1

Q: What are valid values of X, and what does this setting drive?
Router#config t
Router(config)#int f0/0
Router(config-if)#ip ospf priority X
A: 0-255.  Influences OSPF Designated Router selection.  Highest priority wins!  Default = 1, priority = 0 means it won't participate in the election.

Q: What kind of cable would you use to connect a PC to switch, PC to hub, or switch to router?
A: These are dis-similar items, use straight through.

Q: Why would you turn off spanning tree for a given switch port?
A: Atteched to an end node (printer, pc, etc)

Q: Do: turn off spanning tree for ports 3-10
A: #config t
#int range f0/3-10
#spanning-tree portfast
#spanning-tree bpduguard enable   ! NOTE <<

Q: If you do "spanning-tree bpduguard enable" on a port, and someone plugs in a switch to that port, what happens?
A: Port sees a BPDU, shuts down the port by turning it into "error disable".  See that with "show int f0/10"

Q: How do you see if a port is in "error disabled" state, and how do you turn it back on?
A: #show int f0/10
#int f0/10
#shut
#no shut

Q: What is a BPDU?
A: Bridge Protocol Data Units (BPDUs) are frames that contain information about the Spanning tree protocol (STP).

Q: What does VTP stand for?
A: Virtual trunking protocol

Q: What is VTP, what does it do?
A: Virtual Trunking Protocol.  Allows you to create and propagate VLANs, maintains naming consistency of VLAN across all switches. VTP is used when you have multiple VLANs.

Q: How do you see what VTP revision, mode, etc a switch is in?
A: #show vtp status

Q: What are the three VTP operating modes, and what are their capabilities?
A: server (create/modify/delete VLANs, advertises to others, syncs from others)
client (advertises and syncs, but can't change anything)
transparent (create/modify/delete VLANs, configurations are saved in NVRAM, but they are not advertised to other switches)

Q: What are the key pieces of information on the "show vtp status" screen?
A: Configuration revision, VTP operating mode, VTP domain name

Q: Do: change a switch so you can't update VLAN info.
A: #config t
#vtp mode client
#show vtp status

Q: In order to create VLANs, what mode must your switch be in (and do that)?
A: Must be in "VTP server mode".
#config t
#vtp mode server

Q: Do: change vtp domain name of a switch.
A: #vtp domain cisco

Q: Do: configure switch ports f0/1 through f0/10 to be trunk ports.
A: #config t
#int range f0/1-10
#switchport mode trunk

Q: What is the purpose of switchport security?
A: allow X ports access to the network, and then set a violation so if that rule is broken you can shut down the port.

Q: What mode must ports be in if you're doing switchport security?
A: Access mode

Q: How do you see how many MAC addresses have connected to a particular switch port?
A: #show port-security

Q: Do: configure fa ports 1 through 10 on a switch to allow for 2 mac addresses learned dynamically.
A: # int range f0/1-10
# switchport mode access
# switchport port-security
# switchport port-security mac-address sticky  ! added dynamically
# switchport port-security maximum 2
# switchport port-security violation shutdown

Q: What are the three switchport port-security violation modes?
A: Protect: permit traffic from known MAC addresses, drop from unknown
Restrict: same as Protect, and log a syslog message and send SNMP trap, and increment the security violation counter (#show port-security int f0/1)
Shutdown: default, set force the switchport into an error disabled (err-disable) state
faculty(config-if-range)#switchport port-security violation shutdown

Q: What IPv6 address is Anycast address?
A: FC00::

Q: What IPv6 address is Default address?
A: ::

Q: What IPv6 address is EIGRP?
A: ff02::a

Q: What IPv6 address is Global unicast?
A: 2000::/3
routable on public internet, assigned by IANA (Internet Assigned Numbers Authority)

Q: What IPv6 address is Link local?
A: FE80::/10

Q: What IPv6 address is Loopback?
A: ::1

Q: What IPv6 address is Multicast addresses?
A: FF00::/8

Q: What IPv6 address is used for OSPFv3 multicast?
A: ff02::5 to ff02::6

Q: What IPv6 address does RIPNG use?
A: ff02::9

Q: What IPv6 address is Unique Local addresses?
A: FC00::/7
Unique local addresses are available for use in private networks, e.g. inside a single site or organization or spanning a limited number of sites or organizations. They are not routable in the global IPv6 Internet.

Q: What is IPv6 2000::/3?
A: Global unicast
routable on public internet, assigned by IANA (Internet Assigned Numbers Authority)

Q: What is IPv6 ::1?
A: Loopback

Q: What is IPv6 ::?
A: Default address

Q: What is IPv6 FC00::/7?
A: Unique Local addresses.
Available for use in private networks, e.g. inside a single site or organization or spanning a limited number of sites or organizations. They are not routable in the global IPv6 Internet.

Q: What is IPv6 FC00::?
A: Anycast address

Q: What is IPv6 FE80::/10?
A: Link local

Q: What is IPv6 FF00::/8?
A: Multicast addresses

Q: What is IPv6 ff02::5 to ff02::6?
A: OSPFv3

Q: What is IPv6 ff02::9?
A: RIPNG

Q: What is IPv6 ff02::a?
A: EIGRP

Q: What protocol does 802.1Q replace?
A: ISL, Inter Switch Link

Q: For the CCNA exam, what layer will you create ACLs at?
A: Layer 3

Q: Do: config a router for inter-vlan routing, single line plugged in to f0/0.  Need to connect VLAN 10 and 20 (192.168.10.0/24 and .20.0/24 networks)
A: # int f0/0
# no shut   !must do this
# int f0/0.10  !name doesn't need to match VLAN ID
# encapsulation dot1Q 10  !10 is the VLAN ID
# ip address 192.168.10.254 255.255.255.0
# int f0/0.20
# encapsulation dot1Q 20  !VLAN ID
# ip address 192.168.20.254 255.255.255.0

Q: Do: config a switch to be the Root Bridge in an ethernet network containing VLANs 1, 10, and 20
A: #config t
#spanning-tree vlan 1,10,20 priority 0

Q: Do: configure a switch with VLANs "students" and "faculty", and ensure that these VLANs propagate out to other switches on the network (make any assumptions needed for this)
A: #config t
#vtp domain cisco   ! required to propagate!
#vtp mode server
#vlan 10
#name students
#vlan 20
#name teachers
#exit
#int range f0/23-24
#switchport mode trunk

Q: What are the basics of ACLs that you should know?
A: - is read in order until it makes a match. ordered from specific to general; on top, most specific, on bottom most general
- has an implicit deny at the end
- you can only have 1 ACL per interface, per protocol, per direction
- you cannot remove a numbered ACL that lies within the group
- use wildcard mapping

Q: Give some Standard ACL limitations.
A: - numbers from 1-99
- you can only limit the source address (can't use anything else!)
- placed near the destination so needless traffic occurs before it gets there

Q: Where should you put a standard access list?
A: As close to the destination as possible! A standard access-list can only filter using the source ip address.  If it is placed near the source you may limit this source ip address for your entire network rather than for a particular destination.

Q: Do: In the below topology, use a standard access list to prevent anything in the .10.0/24 and .20.0/24 networks (on VLAN 10 and 20) from accessing management VLAN 1.
A: First create the access list:
#config t
#access-list 1 deny 192.168.20.0 0.0.0.255
#access-list 1 deny 192.168.10.0 0.0.0.255
#access-list 1 permit any  !needed to prevent the implicit deny
Then apply it as close to the destination as possible
#int f0/0.1
#ip access-group 1 out !Note direction
... exit/exit/copy run start
For the direction: it's already in the router, prevent it from going out!

Q: Do: see what ACLs are applied to interface f0/0.1.
A: # show ip int f0/0.1

Q: What are the two ways to create a standard ACL to permit host 192168.10.1 to access something?
A: # access-list 1 permit 192.168.10.1 0.0.0.0
# access-list 1 permit host 192.168.10.1

Q: Do: permit 192.168.10.1 to telnet into a router.
A: # config t
# access-list 2 permit 192.168.10.1 0.0.0.0
# line vty 0 15
# access-class 2 in   ! Note direction!
... exit exit copy run start ...

Q: Give some notes on Extended Access Lists, and a sample line
A: - Number 100-199
- place it nearest the source
- can include protocols, source and dest addresses, and port numbers
# access-list 100 permit tcp host 192.168.1.1 host 1.1.1.1 eq 80
! source destination port (http)

Q: Where should an extended access list be placed?
A: An extended access list is placed nearest the source (direction = in); however, check all the inputs to a router, b/c there might be other entry interfaces, in which case you'd need to block the output!

Q: Do: allow 192.168.1.1 to connect to 1.1.1.1 over port 80, block everyone else from port 80; don't block any other traffic.
A: # access-list 100 permit tcp host 192.168.1.1 host 1.1.1.1 eq 80 !source to destination
# access-list 100 deny tcp any host 1.1.1.1 eq 80   !any source to destination
# access-list 100 permit ip any any

Q: Do: apply the following ACL to a router so that traffic doesn't exit the router on f0/0.
# access-list 100 permit tcp host 192.168.1.1 host 1.1.1.1 eq 80 !source to destination
# access-list 100 deny tcp any host 1.1.1.1 eq 80   !any source to destination
# access-list 100 permit ip any any
A: #config t
#int f0/0
#ip access-group 100 out   !out, b/c already _in_ the router!

Q: What are the three different types of NAT (Network Address Translation)?
A: - static NAT: a one-to-one mapping, have to purchase public IPs.  "ip nat inside source static <privateIP> <publicIP>"
- dynamic NAT: buy one external IP per internal IP, and then use that as a pool (gets dynamically assigned)
- NAT overload: the most popular (aka PAT, Port Address Translation), changes source port number, maps to single external IP

Q: You have a private network, and want machines to be able to go out over the net.  What do you use for that?
A: Private IP addresses are not routable on a public interfaces, so use NAT.

Q: When you send an IP packet, you need the source and dest IPs.  With NAT, what are these IPs called?
A: - Inside: IP inside your network; outside: IP outside the network
- Local: how your system understands IPs (localized); global: how the rest of the world understands your IPs (globalized)
So:
inside local: internal IP address, represented in "local" form
inside global: internal IP address translated to esperanto for the external world
outside local: external "real world" IP address represented in "local" form
outside global: external "real world" IP represented in global form

Q: Do: Set up NAT overload to map computers in 192.168.0.0/24 network (on f0/0) to go out on interface s0/0/0.
A: # configure terminal
# interface fastethernet0/0
# ip nat inside
# interface serial0/0
# ip nat outside
# exit
# access-list 1 permit 192.168.0.0 0.0.0.255  !standard ACL
# ip nat inside source list 1 interface serial 0/0 overload

Q: Do: Set up NAT overload to map computers in 192.168.0.0/24 network (on f0/0) to go out on interface s0/0/0 (1.1.1.0/24) using a pool!
A: # configure terminal
# interface fastethernet0/0
# ip nat inside
# interface serial0/0
# ip nat outside
# exit
# ip nat pool laz 1.1.1.254 1.1.1.254 netmask 255.255.255.0
# access-list 1 permit 192.168.0.0 0.0.0.255  !standard ACL
# ip nat inside source list 1 pool laz overload

Q: Do: Set up dynamic NAT to map computers in 192.168.0.0/24 network (on f0/0) to go out on interface s0/0/0 (1.1.1.0/24) with a pool of 200 IPs
A: # configure terminal
# interface fastethernet0/0
# ip nat inside
# interface serial0/0
# ip nat outside
# exit
# ip nat pool R1POOL 1.1.1.1 1.1.1.200 netmask 255.255.255.0
# access-list 1 permit 192.168.0.0 0.0.0.255  !standard ACL
# ip nat inside source list 1 pool R1POOL
Probably should add "overload" - the netmask has 254 hosts, but the pool only has 200 IPs!

Q: What are some common pitfalls to look out for in dynamic and overload NAT?
A: - pool name case-sensitive
- access-list number not matching
- need "overload" for overloading :-D
- bad wildcard mask
- forgot to ip nat inside/outside, or on the wrong side
- bad pool size

Q: what is a wan?
a) distance between locations
b) speed used to connect source and destination
c) you lease a wan
d) you own a wan.
A: C).  According to Cisco, distance is not the deciding factor if you own the equipment, it's considered a LAN.

Q: What layers do WANs work at?
A: Layer 1 and 2

Q: What are the three WAN connection types?  Give some very brief notes for each
A: Dedicated (leased lines, aka point-to-point): a pre-established WAN communications from CPE (cust premises equipment) through DCE switch then to CPE.  Expensive.  uses synchronous serial lines up to 45 Mbps.  HDLC and PPP encapsulations.
Circuit switching: phone call.  Cheap, plain old telephone service (POTS) and ISDN dial-up connections.  Low-bandwidth data transfers.
Packet Switching: share bandwidth with other companies to save money, just like a super old party line, where homes shared the same phone number and line to save money.  Will only really work for you if your data transfers are bursty, not continuous.  Frame Relay, X.25 (nobody uses this), or MPLS are packet-switching technologies with speeds that can range from 56 Kbps up to T3 (45 Mbps).

Q: What is the default encapsulation for serial connections?
A: HDLC (High-level Data Link Control) - each vendor implements it differently.

Q: If you have 2 routers from 2 different vendors, what encapsulation should you use for a serial connection?
A: PPP.  Using HDLC will end up with a layer 2 issue, since different vendors implement HDLC differently.
Use HDLC if they were from the same vendor.

Q: WAN terminology: Customer premises equipment (CPE)
A: Customer premises equipment (CPE) is equipment that’s typically owned by the subscriber and located on the subscriber’s premises.

Q: WAN terminology: Demarcation point
A: The demarcation point (demarc for short) is the precise spot where the service provider’s responsibility ends and the CPE begins. It’s generally a device in a telecommunications closet owned and installed by the telecommunications company (telco). It’s your responsibility to cable (extended demarc) from this box to the CPE, which is usu- ally a connection to a CSU/DSU, although more recently we see the provider giving us an Ethernet connection. Nice!

Q: WAN terminology: Local loop
A: The local loop connects the demarc to the closest switching office, referred to as the central office.

Q: WAN terminology: Central office (CO)
A: This point connects the customer’s network to the provider’s switch- ing network. Make a mental note that a central office (CO) is sometimes also referred to as a point of presence (POP).

Q: WAN terminology: Toll network
A: The toll network is a trunk line inside a WAN provider’s network. This net- work is a collection of switches and facilities owned by the Internet service provider (ISP).

Q: What are the rate-related terms for Frame Relay?
A: CIR (Committed information rate) The maximum bandwidth of data guaranteed to be delivered. It’s the average amount that the service provider will allow you to transmit.
If you exceed the CIR (can go up to the Access rate), but bits will be tagged as "DE", "Discard Eligible"
Access rate: The maximum speed at which the Frame Relay interface can transmit.  eg, T1 line.  You can exceed the CIR (will be marked as DE), up to the Access rate, *if that bandwidth is available*)

Q: If your router's s0/0/0 port is going out to a WAN, what's wrong with the below config?
#int s0/0/0
#ip address x.x.x.x y.y.y.y
#clock rate 4000000
#no shut
A: The provider sets the clock rate.

Q: What is a DLCI?
A: Frame Relay DLCI: Data Link Connection Identifier.  A PVC (permanent virtual circuit).  Your provider gives you a DLCI number, which identifies you to the cloud.  The DLCI is a local number.

Q: What type of network is Frame Relay?
A: Frame Relay is a non-broadcast multi-access network

Q: Is a router DCE or DTE by nature?
A: DTE.  Your provider is the DCE and provides the clock rate.

Q: What is a CSU/DSU?
A: A Layer 1 (deals with bits) digital-interface device used to connect a data terminal equipment (DTE), such as a router, to a digital circuit, such as a Digital Signal 1 (T1) line.
The CSU/DSU implements two different functions. The channel service unit (CSU) is responsible for the connection to the telecommunication network, while the data service unit (DSU) is responsible for managing the interface with the DTE.

Q: What is the signaling standard used between routers and Frame Relay switches, and what versions are there?
A: Local Management Interface (LMI). Communication takes place between a router and the first frame relay switch it's connected to. Information about keepalives, global addressing, IP Multicast and the status of virtual circuits is commonly exchanged using LMI.
ANSI, Q933A (ITU-T), Cisco

Q: Below is a hub-and-spoke network connected with Frame Relay.  Give some *very basic* points about setting it up.
A: - LMI between routers and cloud
- DLCIs for each router-to-cloud line - locally significant!
- subinterfaces on the AZ router to talk to each DLCI (best)

Q: Below is a multipoint design of Frame Relay.  What is the potential problem with this?
A: Split Horizon.  MO will tell AZ about its networks, but AZ will not broadcast it back out S0/0 as that could cause a routing loop.  As a result, TX and CA won't learn about the network.  Could disable split horizon, but that might get messy.

Q: Routers R1-3 all have RIP enabled.  DLCI 102 and 103 are on R1's s0/0/0 interface (not subinterfaces!), and connect to R2 and R3 respectively.  R2 has DLCI 201, and R3 has 301, back to R1.  Configure frame-relay on R1 so that RIP can make it over the WAN (don't worry about split horizon)
A: # router rip / version 2 / no auto-summary ... etc
# int s0/0/0
# ip address 10.0.0.1 255.255.255.252
# encapsulation frame-relay
# bandwidth 64
# frame-relay map ip 10.0.0.2 102 broadcast
# frame-relay map ip 10.0.0.3 103 broadcast   !remote ip, local DLCI
# no shut

Q: For the below topology, set up Frame Relay with subinterfaces.  R1 connects to R2, and R1 to R3, via the cloud.
A: ! R1
! s0: encapsulation under physical interface, no address
# int s0/0/0
# encapsulation frame-relay
# no shut
! Add 102 pt-to-pt
# int s0/0/0.102 point-to-point
# frame-relay interface-dlci 102
# ip address 10.0.0.1 255.255.255.0
! 103 subint
# int s0/0/0.103 point-to-point
# frame-relay interface-dlci 103
# ip address 10.0.1.1 255.255.255.0
... exit exit copy run start
! R2
# int s0/0/0 point-to-point
# encapsulation frame-relay
# frame-relay interface-dlci 201
# ip address 10.0.0.2 255.255.255.0
# no shut
! R3
# int s0/0/0 point-to-point
# encapsulation frame-relay
# frame-relay interface-dlci 301
# ip address 10.0.1.2 255.255.255.0
# no shut

Q: What command will show you the signalling method that the router is using to communicate with the frame relay service provider?
A: # show frame-relay lmi
LMI Statistics for interface Serial0/0/0 (Frame Relay DTE) LMI TYPE = CISCO
_ Invalid Unnumbered info 0      Invalid Prot Disc 0
_ Invalid dummy Call Ref 0       Invalid Msg Type 0

Q: Packets are being dropped/delayed from A to B.  How can you check what's going on, what should you look for?
A: Look for FECN (Forward Explicit Congestion Notification) and BECN (Backward Explicit Congestion Notification) with "show frame-relay pvc"
If that switch encounters transmission delays due to network congestion, the switch will set the FECN bit on the frames heading for Router B, since that's the direction in which the frames are traveling.  The BECN bit will be set on frames being sent back to Router A.

Q: How do you see what what IPs a DLCI is going to on your router, and which destination IPs are reachable via Frame Relay?
A: # show frame-relay map
_R1#show frame-relay map
_Serial0/0/0.102 (up): point-to-point dlci, dlci 102, broadcast, status defined, active
_Serial0/0/0.103 (up): point-to-point dlci, dlci 103, broadcast, status defined, active

Q: If you have two Cisco routers with a point-to-point connection, what is the default WAN protocol, and what are potential downsides and remedy?
A: HDLC is default; downside if one router goes down could want to put in a non-cisco router but then HDLC wouldn't work due to vendor-specific implementation of HDLC; could use PPP which is open standard.

Q: What are the main components of PPP?
A: EIA/TIA-232-C, V.24, V.35, and ISDN - A Physical layer international standard for serial communication.
HDLC-like framing for transporting multiprotocol packets over point-to-point links.
Extensible Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connection.
Family of Network Control Protocols (NCPs) for establishing and configuring different network layer protocols. PPP allows the simultaneous use of multiple network layer protocols. Some of the more common NCPs are Internet Protocol (IPv4) Control Protocol, IPv6 Control Protocol, AppleTalk Control Protocol, ... etc
the PPP protocol stack is specified at the Physical and Data Link layers only.

Q: What are the different OSPF LSA types needed for the exam?
A: Type 1 LSA: router link advertisement (RLA), or just router LSA.  Sent by every router to other routers in its area. Contains the status of a router’s link in the area to which it is connected.  Router in multiple areas sends multiple LSAs. Type 1 LSAs contain the router ID (RID), interfaces, IP information, and current interface state.
Type 2 LSA: network link advertisement (NLA).  Generated by designated routers (DRs).  Contains information about the state of other routers that are part of the same network, and DR and BDR IP info.  Only flooded to all routers that are in the same area as the one containing the specific network.
Type 3 LSA: summary link advertisement (SLA), generated by area border routers (ABR).  A summary of information about the networks in an area, sent to area 0 which then sends it to all other routers.
Type 4 LSA: ASBR-Summary LSA, generated by an ABR to describe route(s) to an ASBR (autonomous system border router) in the ABR's area to outside neighboring routers. For example an ABR telling Area 0 that an ASBR is located inside Area 1.
Type 5 LSA: AS external link advertisements, advertises routes that are external to the OSPF autonomous system, flooded everywhere.  Generated for each individual external network advertised by the ASBR.

Q: What are the different OSPF network types?
A: Point-to-point; point-to-multipoint (hub and spokes); multi-access (mesh).
Broadcast; non-broadcast.
Multi-access means we have to select a DR and BDR.
Non-broadcast means that OSPF expects us to configure neighbors ourselves.
...
Broadcast (multi-access): eg Ethernet.  DR and BDR must be elected for each broadcast multi-access network, we don't have to configure anything.
Nonbroadcast multi-access (NBMA): networks such as Frame Relay, X.25, and Asynchronous Transfer Mode (ATM). These types of networks allow for multi-access without broadcast ability like Ethernet.
Since this is non-broadcast, we won't be able to dynamically discover our neighbors, we have to designate them.  We do need a DR and BDR, but have to pick the them strategically; eg, below, R1 *must* be configured as the DR as that's the only router adjacent to all routers, and R2,3,4 must not be elected so we set their OSPF priority to 0.  Note here, there is no BDR, there can't be a BDR because no other router has adj. to everyone.
￼￼
Point-to-point: direct connection between two routers that provides a single communication path.  Can be physical (eg cable) or logical (eg Frame Relay). No DR/BDR, since there's only 2 routers and there's no need for scalability.
Point-to-multipoint: a group of separate connections between a single interface on one router and multiple destination routers. All interfaces on all routers share the point-to-multipoint connection and belong to the same network. Since this is point-to-point, you don't need DR/BDR, and you don't need to discover neighbors.
Further broken down by broadcast or non-broadcast, which defines the kind of OSPF configurations you can deploy.

Q: What are the PPP states?
A: DEAN O.T.
Link Dead: Default state; physical layer not connected.
Link Establishment: Physical layer connected, basic configuration of link performed by LCP.
Authentication: Basic link is now opened, and optional authentication of device is performed.
Network-Layer Protocol: One or more NCPs open an NCP link within the LCP link.
Link Open: Link is open and operating normally.
Link Termination: LCP link is shut down.
The PPP Link Configuration Protocol (LCP) is generally in charge of setting up and maintaining PPP links. LCP may invoke an authentication protocol (PAP or CHAP) when PPP is configured to use authentication. After an LCP link has been opened, PPP invokes one or more Network Control Protocols (NCPs) for the layer three protocol being carried on the link. These perform any network-layer-specific configuration needed before the link can carry that particular network layer protocol.

Q: What is PPP (for serial lines)?
A: Point-to-Point Protocol (PPP), which defines a complete method for robust data link connectivity between units using serial lines or other physical layers. It includes numerous capabilities and features, including error detection, compression, authentication, encryption and much more.

Q: What are the two Point-to-Point Protocol (PPP) authentication protocols?
A: Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP)
PAP: Passwords are sent across the link in clear text.  Not secure. Still useful though: A large installed base of client applications that do not support CHAP, CHAP may be incompatible
CHAP: challenge-response.  User password is never sent across the connection

Q: Do: configure PPP with authentication for these routers (assume IPs already set):
A: on R1:
# username R2 password cisco   !the other router!
# int s0/0/0
# encapsulation ppp
# ppp authentication chap pap
on R2:
# username R1 password cisco
# int s0/0/0
# encapsulation ppp
# ppp authentication chap pap

Q: What are some network redundancy protocols?
A: VRRP (Virtual Router Redundancy Protocol).  (industry standard) - IETF in 1999, multiple vendors, faster timers hello 1s, hold 3s.  Enables a group of routers on a LAN segment to form a single virtual router (a VRRP group).  Master router and backup routers.
HSRP (Hot Standby Router Protocol).  Cisco proprietary created 1994, default hello timers 3 s and hold timer 10 s (can configure these).  Works on active (higher priority) and standby routers, with virtual gateway and virtual ip address
GLBP (Gateway Load Balancing Protocol).  Cisco only.  Just like HSRP - creates multiple virtual mac addresses.   Has load balancing

Q: Do: set the following switches so that both lines are used, resulting in a bigger pipe.
A: Use etherchannel!
! Add lines to channel
# int range g0/1-2
# channel-group 1 mode active   ! using Link Aggregation Protocol (LACP)
! Trunk it
# int port-channel 1
# switchport mode trunk
# exit
And then do the same on the other side.

Q: How does HSRP (Hot Standby Router Protocol) determine the active router?
A: Priority, highest priority wins
(config)# int f0/0
(config-if)# standby 1 ip 192.168.1.100  ! group, and virtual IP
(config-if)# standby 1 priority 105
if tied, highest IP.

Q: The host can ping server 1.1.1.1, but it doesn't have redundancy for the routers.  Set up HSRP on the routers.
A: on R1:
# int f0/0
#standby 1 ip 192.168.1.100   ! group, and virtual IP
#standby 1 priority 105   !active
#standby 1 preempt   !overthrow lower priority routers if  I come back online
#standby 1 track f0/1   ! decrements the priority if that interface goes down
on R2:
#int f0/0
#standby 1 ip 192.168.1.100
#standby 1 priority 100   !standby
#standby 1 track f0/1

Q: How do I see the state of my HSRP router?
A: # show standby
_FastEthernet0/0 - Group 1 (version 2)
_  State is Active
_    16 state changes, last state change 00:41:35
_  Virtual IP address is 192.168.1.100
_  Active virtual MAC address is 0000.0C9F.F001
_    Local virtual MAC address is 0000.0C9F.F001 (v2 default)
_  Hello time 3 sec, hold time 10 sec
_    Next hello sent in 0.479 secs

Q: What are the virtual MAC addresses for HSRP?
A: version 1: 0000.0C07.ACxy, where xy is the HSRP group number in hex; eg HSRP group 1 uses the HSRP virtual MAC address of 0000.0C07.AC01.
version 2: range of 0000.0C9F.F000 to 0000.0C9F.FFFF.
Both start with 0000.0C, for Cisco.

Q: Give some notes about VRRP
A: Essentialy the same as HSRP, with the following notes:
- active/standby now master/backup
- standby group is vrrp group
- master router can share the virtual IP
- 1 sec hello, 3sec down time (no config)
- advertise/learn master only

Q: You have 3 routers on a switch, each in 192.168.1.0/24 network, .1-.3.  Config interfaces and redundancy using VRRP.  Make whatever assumptions needed.
A: R1(config)#interface FastEthernet0/0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R1(config-if)#vrrp 10 ip 192.168.1.1  ! Equals actual IP, so this becomes the master
R1(config-if)#vrrp 10 preempt
R2(config)#interface FastEthernet0/0
R2(config-if)#ip address 192.168.1.2 255.255.255.0
R2(config-if)#vrrp 10 priority 110
R2(config-if)#vrrp 10 ip 192.168.1.1
R3(config)#interface FastEthernet0/0
R3(config-if)#ip address 192.168.1.3 255.255.255.0
R3(config-if)#vrrp 10 priority 100
R3(config-if)#vrrp 10 ip 192.168.1.1
# show vrrp

Q: Give some notes about GLBP
A: - cisco-proprietary
- allow automatic selection and simultaneous use of multiple available gateways, as well as permit automatic failover between those gateways
- every router is active (load-balancing, host-dependent, round-robin (most popular), or weighted)
- single virtual IP, with multiple MAC addresses
- Active Virtual Gateway, other routers act as active virtual forwarders

Q: Config GLBP on int f0/0, with virtual IP 10.1.1.20
A: GLBP1(config)#int fa0/0
GLBP1(config-if)#glbp 1 ip 10.1.1.20
GLBP1(config-if)#glbp 1 name GLBP_Test
GLBP1(config-if)#GLBP 1 priority 110

Q: What are the different versions of SNMP?
A: SNMPv1
- community strings (read, or read/write) - plaintext
- UDP
SNMPv2c
- Provides GET BULK to minimize GETS
- not more secure than v1 (community strings)
- Includes enhancements of SNMPv1 in the areas of protocol packet types, transport mappings, MIB structure elements
- uses existing SNMPv1 administration structure.  It uses UDP, can use TCP.
SNMPv3
- authentication with MD5 or SHA
- encryption and data integrity with DES or DES-256 encryption
GET BULK is supported.  Uses TCP.

Q: What does SNMP query?
A: It queries the Management Information Base (MIB), a collection of information that’s organized hierarchically and can be accessed by protocols like SNMP.
Organizational IDs (OIDs) are laid out as a tree with different levels assigned by different organizations, with top-level MIB OIDs belonging to various standards organizations.

Q: Do: configure SNMP with a name of "sparta" on a router so that the router can be asked for information.  Should be read-only.
A: #config t
#snmp-server community sparta ro

Q: What are the syslog severity levels?
A: Every Awesome Cisco Engineer Will Need Icecream Daily
emergencies (severity 0) - system unusable
alerts (sev 1) - needs immediate attention
critical (sev 2) - should be addressed
errors (sev 3) - error, but system not unusable
warnings (sev 4) - operation failed to successfully complete
notifications (sev 5) - admin notification about a change to the system
informational (sev 6) - normal system operation
debugging (sev 7) - very detailed

Q: Do: config a router to send debugging (sev 7) syslog messages to host 1.1.1.1 and 2.2.2.2
A: #logging 1.1.1.1
#logging 2.2.2.2
#logging trap debugging
#exit
#copy run start

Q: Do: someone on the network is hogging bandwidth.  Set up a simple system to watch what's happening in the network.
A: Set up netflow on the interface
R1(config)#int f0/0
R1(config-if)#ip flow ingress
R1(config-if)#ip flow egress
R1(config-if)#exit
Forward these logs!
R1(config)#ip flow-export destination 192.168.1.1 9996
R1(config)#ip flow-export version 9   !1, 5, or 9
9996: packet tracer's UDP for the collector

Q: Which parameter or parameters are used to calculate OSPF cost in cisco routers?
A: Bandwidth

Q: What is the default maximum number of equal-cost paths that can be placed into the routing of a cisco OSPF router?
A: 4
http://www.freeccnaworkbook.com/workbooks/ccna/configuring-ospf-maximum-paths

Q: What is the main function of the OSI Application Layer?
A: Identifying and confirming the communication partner’s availability and verifying the required resources to permit the specified type of communication.

Q: What is the main function of the OSI Presentation Layer?
A: It presents data to the Application layer and is responsible for data translation and code formatting.  include protocols that define how standard data should be formatted, and handles data compression, decompression, encryption, and decryption

Q: What is the main function of the OSI Session Layer?
A: setting up, managing, and dismantling sessions between Presentation layer entities and keeping user data separate. Dialog control between devices also occurs at this layer.

Q: What is the main function of the OSI Transport Layer?
A: The segments and reassembles data into a single data stream. Services located at this layer take all the various data received from upper-layer applications, then combine it into the same, concise data stream. The term reliable networking can be used: acknowledgments, sequencing, and flow control will all be used.

Q: What is the main function of the OSI Network Layer?
A: manages device addressing, tracks the location of devices on the network, and determines the best way to move data.
connection services - packet reordering; switching (3 types: packet, circuit, message)

Q: What is the main function of the OSI Data Link Layer?
A: provides for the physical transmission of data and handles error notification, network topology, and flow control. Ensures that messages are delivered to the proper device on a LAN using hardware addresses and will translate messages from the Network layer into bits for the Physical layer to transmit.  Formats the message, each called a data frame, and adds a customized header containing the hardware destination and source address.
Media Access Control (MAC) Defines how packets are placed on the media. Contention media access is “first come/first served” access where everyone shares the same band- width—hence the name. Physical addressing; logical topologies.  Line discipline, error notification (but not correction), the ordered delivery of frames, and optional flow control can also be used at this sublayer.  CSMA/CD.
Logical Link Control (LLC) - identifying Network layer protocols and then encapsulating them.  Tells the Data Link layer what to do with a packet once a frame is received. It works like this: a host receives a frame and looks in the LLC header to find out where the packet is destined—for instance, the IP protocol at the Network layer. The LLC can also provide flow control and sequencing of control bits.  Connection service, synchronizing (isochronous (look to external device), asynchronous (look to own internal clock), synchronous).

Q: What is the main function of the OSI Physical layer?
A: sends and receives bits. Communicates directly with the various types of actual communication media. The Physical layer specifies the electrical, mechanical, procedural, and functional requirements for activating, maintaining, and deactivating a physical link between end systems.
How bits are represented on medium
Wiring standards
Physical topology
Synchronizing bits
Bandwidth (Broadband - different freqs for different flows; baseband - all freqs for a single communication)
Multiplexing - eg Time Division Multiplexing, each channel has one moment in time; Statistical TDM (multi based on need); Frequency Division Multiplexing (FDM)
This layer is also where you identify the interface between the data terminal equipment (DTE) and the data communication equipment (DCE). (Some old phone- company employees still call DCE “data circuit-terminating equipment.”) The DCE is usually located at the service provider, while the DTE is the attached device. The services available to the DTE are most often accessed via a modem or channel service unit/data service unit (CSU/DSU).

Q: What are the three different communication modes at the session layer?
A: Simplex is simple one-way communication, kind of like saying something and not getting a reply.
Half-duplex is actual two-way communication, but it can take place in only one direction at a time, preventing the interruption of the transmitting device.
Full-duplex is exactly like a real conversation where devices can transmit and receive at the same time, much like two people arguing or interrupting each other during a telephone conversation.

Q: What are the two types of packets used at the Network layer?
A: Data packets: used to transport user data through the internetwork.  Protocols used to support data traffic are called routed protocols (eg IP and IPv6)
Route update packets: used to update neighboring routers about the networks connected to all routers within the internetwork, to build/maintain routing tables. Protocols that send route update packets are called routing protocols (eg RIP).

Q: What steps are needed to establish a connection-oriented session?
A: The first “connection agreement” segment is a request for synchronization (SYN).
The next segments acknowledge (ACK) the request and establish connection parameters—the rules—between hosts. These segments request that the receiver’s sequencing is synchronized here as well so that a bidirectional connection can
be formed.
The final segment is also an acknowledgment, which notifies the destination host that the connection agreement has been accepted and that the actual connection has been established. Data transfer can now begin.

Q: What are the characteristics of a connection-oriented service?
A: A virtual circuit, or “three-way handshake” is set up.
It uses sequencing.
It uses acknowledgments.
It uses flow control.

Q: In OSI transport, what are the types of flow control?
A: buffering, windowing, and congestion avoidance.

Q: What is windowing?
A: The quantity of data segments, measured in bytes, that the transmitting machine sends without receiving an acknowledgment.  The window size starts at 1, and if the receiver ACKS it, the sender doubles the window size, and so on, thereby exploiting the reliability of the connection.

Q: What are FECN and BECN?
A: FECN (Forward Explicit Congestion Notification) and BECN (Backward Explicit Congestion Notification)
Frame relay, use "show frame-relay pvc"

Q: What are the router "names" for the different router redundancy protocols?
A: VRRP: Master and backup, in VRRP Group.
HSRP (Hot Standby Router Protocol).  Active and standby. (Note Hot Standby - so active and standby)
GLBP (Gateway Load Balancing Protocol).  same as HSRP

Q: What is Etherchannel?
A: Port channel technology developed by cisco to group a bunch of redundant links and make them into one logical link.

Q: What are the two ether-channel negotiation protocols?
A: PAgP (Port Aggregation Protocol - Cisco proprietary, sends packets every 30 s)
LACP (Link Aggregation Control Protocol, IEEE802.3ad)

Q: What is Port Channeling?
A: 2 to 8 channels linked into one aggregated channel

Q: When configuring etherchannel, you use, eg "# channel-group 1 mode X".  What are the values of X?
A: active - LACP unconditionally
passive - LACP, waits and responds to active side
desirable - PAgP unconditionally
auto - PAgP, waits and responds to desirable side
on - both sides must be "on" - turns on etherchannel without PAgP or LACP
In general, Auto mode in PAgP is the same as Passive mode in LACP and Desirable mode is same as Active mode.

Q: Do: configure etherchannel so that fast ethernet ports 1-3 carry vlans 1,2, and 5 in one big channel!
A: # int range f0/1-3
# switchport mode trunk
# channel-group 1 mode desirable
# exit
! "desirable" means this is PAgP (desirable and auto)
! the other switch should have that set as desirable or auto
# int port-channel 1
# switchport mode trunk
# switchport trunk allowed vlan x,x,x,x

Q: There are redundant links below - they should be blocked!  What would block them, and why aren't they blocked here?
A: Blocked by SPT; not blocked due to etherchannel

Q: Do: disable DTP (dynamic trunking protocol) on port f0/1
A: # int f0/1
# switchport nonegotiate

Q: What are some possible causes of LAN congestion?
A: Too many hosts in a collision or broadcast domain
Broadcast storms
Too much multicast traffic
Low bandwidth
Adding hubs for connectivity to the network
A bunch of ARP broadcasts

Q: What network devices operate at all seven layers of the OSI model?
A: Network management stations (NMSs)
Web and application servers
Gateways (not default gateways)
Servers
Network hosts

Q: What OSI layer checks on partner availability and resources for communication?
A: Identifying and confirming the communication partner’s availability and verifying the required resources to permit the specified type of communication to take place also occurs at the Application layer.

Q: What is the purpose of Flow Control, and what layer is it on?
A: to provide a way for the receiving device to control the amount of data sent by the sender.
Its job is to ensure data integrity at the Transport layer by allowing applications to request reliable data transport between systems.

Q: What is Layer 2 switching considered?
A: hardware-based bridging because it uses specialized hardware called an application-specific integrated circuit (ASIC). ASICs can run up to high gigabit speeds with very low latency rates.

Q: OSI Model: Which layer chooses and determines the availability of communicating partners along with the resources necessary to make the connection; coordinates partnering applications; and forms a consensus on procedures for controlling data integrity and error recovery?
A: Application layer

Q: OSI model: Which layer ensures the trustworthy transmission of data across a physical link and is primarily concerned with physical addressing, line discipline, network topology, error notification, ordered delivery of frames, and flow control?
A: Data Link layer.  PDUs at the Data Link layer are called frames and provide physical addressing plus other options to place packets on the network medium.

Q: What happens to packets when they get to a router?
A: Each time a packet is sent between routers, it’s framed with control information at the Data Link layer, but that information is stripped off at the receiving router and only the original packet is left completely intact. This framing of the packet continues for each hop until the packet is finally delivered to the correct receiving host.

Q: Which layer provides the physical transmission of the data and handles error notification, network topology, and flow control?
A: Data Link

Q: Ethernet is defined at which OSI layers?
A: Data Link and Physical

Q: 2. With respect to the OSI model, which of the following are correct statements about PDUs?
A. A segment contains IP addresses.
B. A packet contains IP addresses.
C. A segment contains MAC addresses.
D. A packet contains MAC addresses.
A: B. The contents of a protocol data unit (PDU) depend on the PDU as they are created in a specific order and their contents are based on that order. A packet will contain IP addresses but not MAC addresses as MAC addresses are not present until the PDU becomes a frame.

Q: 14. An example of a device that operates on the physical layer is a ____________. A. Hub B. Switch C. Router D. Bridge
A: A. Hubs operate on the Physical Layer as they have no intelligence and send all traffic in all directions.

Q: What does HDLC stand for? (serial connections)
A: HDLC (High-level Data Link Control)

Q: What are the main components in SNMP?
A: Three key components:
A managed device is a node that has an SNMP agent and resides on a managed network. These devices can be routers and access servers, switches and bridges, hubs, computer hosts, or printers.
An agent is a software module residing within a device. This agent translates information into a compatible format with SNMP.
A network-management system (NMS) runs monitoring applications.  The NMS sends out a request and the managed devices return a response

Q: What is an “SNMP Community String”?
A: “SNMP Community string” is like a user id or password that allows access to a router's or other device's statistics.
SNMP Community strings are used only by devices which support SNMPv1 and SNMPv2c protocol. SNMPv3 uses username/password authentication, along with an encryption key.

Q: What happens when a collision happens on Ethernet?
A: 1. A jam signal informs all devices that a collision occurred.
2. The collision invokes a random backoff algorithm.
3. Each device on the Ethernet segment stops transmitting for a short time until its back-off timer expires.
4. All hosts have equal priority to transmit after the timers have expired.

Q: What special setting must be made for the port going to the Hub below?
A: Must be set to half-duplex for collision detection to occur.

Q: What happens when a full-duplex Ethernet port is first powered on?
A: It first connects to the remote end and then negotiates with the other end of the Fast Ethernet link. This is called an auto-detect mechanism. This mechanism first decides on the exchange capability, which means it checks to see if it can run at 10, 100, or even 1000 Mbps. It then checks to see if it can run full-duplex, and if it can’t, it will run half-duplex.
* There are no collisions in full-duplex mode.
* A dedicated switch port is required for each full-duplex node.
* The host network card and the switch port must be capable of operating in full- duplex mode.

Q: What's the layout of a MAC address?
A: 6 bytes, hex.  3 organizationally unique identifier (OUI), 3 NIC. eg, 12-34-56-aa-bb-cc
Media Access Control (MAC), or hardware, address, burned into every Ethernet network interface card (NIC).

Q: What is the format of an Ethernet_II Frame (at the data link layer)?
A: SFD - Start Frame Delimiter
Dest & Source are MAC addresses
FCS - Frame Check Sequence
Packets Stored Discreetly So They Don't F**k

Q: What can a straight-through cable connect?
A: Host to switch or hub
Router to switch or hub
Think about a regular host -> switch -> router network -- these are all straight-through.

Q: What can a crossover cable connect?
A: Like items
Switch to switch
Hub to hub
Host to host
Hub to switch
Router to router
and Router direct to host

Q: What layer of the OSI uses port numbers?
A: The Transport layer uses port numbers to define both the virtual circuit and the upper-layer processes.

Q: When using a connection-oriented protocol like TCP, the Transport layer takes the data stream, makes segments out of it, and establishes a reliable session by creating what?  What defines that thing?
A: A virtual circuit, called a socket.  Defined by the source and destination port number plus the source and destination IP address.

Q: Compare full- and half-duplex Ethernet
A: Full-duplex Ethernet:
- uses two pairs of wires at the same time
- can send and receive at the same time, using different wires to eliminate collisions
- devices at both ends of the cable must be capable of and configured to perform full-duplex (device will try to autodetect)
Half:
- uses one wire pair
- can send or receive but not at the same time and still can suffer collisions

Q: What are the IEEE physical standards for cabling?
A: These standards describe the capabilities and physical characteristics of various cable types and include but are not limited to 10Base-2, 10Base-5, and 10Base-T.

Q: What cables should be used below?  If the console was replaced by a host, what would it be?  If one of the spoke switches was a hub, what would it be?
A: straight-through: different; crossover: similar
host-switch: straight-through
switch-switch: crossover
switch-router: straight-through
router-console: rollover
router-host: crossover
switch-hub: crossover

Q: When the I/G bit in a MAC address is set to 1 the transmission is ... what?
A: Broadcast, or Multicast.  That means "Individual/Group Bit", so if it's 1, it's a group!

Q: What are the correct settings when configuring a term emulation program?
A: Bits per sec: 9600
Data bits: 8
Parity: none
Stop bits: 1
Flow control: none

Q: True or false: there are very few collisions in full-duplex mode.
A: False, there are no collisions.

Q: What are the steps taken when a host wants a DHCP-leased address? ipv4
A: DORA
1. The DHCP client broadcasts a DHCP Discover message looking for a DHCP server (Port 67).
2. The DHCP server that received the DHCP Discover message sends a layer 2 unicast DHCP Offer message back to the host.  (DHCP server checks for conflicts using the Ping)
3. The client then broadcasts to the server a DHCP Request message asking for the offered IP address and possibly other information.
4. The server finalizes the exchange with a unicast DHCP Acknowledgment message.
client sends gratuitous ARP to check ... at some point.

Q: What are the other names for the TCP/IP model layers?
A: Process/Application layer
Host-to-Host layer/or Transport
Internet layer
Network Access layer/or Link

Q: What's the TCP segment format?
A: Don't have to memorize this, but good to be aware.
sequence and ack for connection-oriented communication

UDP segment format

Q: When putting together a TCP segment, the source and destination ____ are set.  What are their values?
A: Ports.  Source port is dynamically assigned, starts at 1024.

Q: What are protocols that use UDP?
A: SNMP 161, TFTP 69, DNS 53, BooTPS/DHCP 68
(DNS also uses TCP)

Q: What is the format of an IP header?
A: Note Time to live - decrements on every router hop

Q: What is Ethernet?
A: A link layer protocol in the TCP/IP stack.  Describes:
- how networked devices can format data for transmission to other network devices on the same network segment
- how to put that data out on the network connection. Touches Physical and Data Link layers.
At Data Link layer: responsible for Ethernet addressing, aka MAC or hardware addressing. Responsible for framing packets received from the Network layer and preparing them for transmission on the local network through the Ethernet contention-based media access method.

Q: Give some quick-n-dirty facts about Cat-x cables
A: Cat 3: 10 Mbps
Cat 5: 100 Mbps
Cat 5e/6: 1000 Mbps
UTP (Unshielded Twisted Pair) Cable maximum distance: 100 Meters
The standard connector in computer networking is an RJ45.

Q: Drop some factbombs about fibre optics
A: Standard Max Distance
1000BASE-SX: 220 or 550 meters
1000BASE-LX: 550 meters
1000BASE-LX/LH (Single-mode): 10 km
1000BASE-ZX: 70 km
SLLZ - SLLLLLEAZY - NuNS + LiLies, Lilies, Toes, Kiss
BASE = "baseband signalling", only Ethernet signals

Q: What wiring is used for Fast Ethernet and Gig Ethernet?
A: 10BASE-T - Cat3, Ethernet
100BASE-TX - Cat5, Fast Ethernet
1000BASE-T - Cat5, Gigabit Ethernet
BASE = "baseband", T = Twisted

Q: What are the protocol numbers for ICMP, TCP, and UDP, EIGRP, OSPF?
A: ICMP = 1   (I looks like a 1)
TCP = 6    (SH!  - forces everyone to listen)
UDP = 17   (TalK - talking without people necessarily hearing)
EIGRP = 88 (FiVe letters)
OSPF = 89  (FaP for ospf)

Q: What are some host-to-host layer protocols?
A: Transmission Control Protocol (TCP)
User Datagram Protocol (UDP)

Q: What is the most important layer of the DoD model?
A: All network roads don’t lead to Rome—they lead to IP. And all the other protocols at this layer, as well as all those at the upper layers, use it. Never forget that. All paths through the DoD model go through IP.

Q: What are characteristics of ICMP packets?
A: - They can provide hosts with information about network problems
- They are encapsulated within IP datagrams

Q: What are some common events that ICMP relates to?
A: Destination unreachable
Buffer full/source quench
Hops/time exceeded
Ping
Traceroute
Note: even though ICMP works at the Internet (Network) layer, it still uses IP to do the Ping request!  :-)

Q: What are the different IPv4 address types?
A: Loopback (localhost) Used to test the IP stack on the local computer. Can be any address from 127.0.0.1 through 127.255.255.254.
Layer 2 broadcasts These are sent to all nodes on a LAN. Broadcasts (layer 3) These are sent to all nodes on the network.
Unicast This is an address for a single interface, and these are used to send packets to a single destination host.
Multicast These are packets sent from a single source and transmitted to many devices on different networks. Referred to as “one-to-many.”

Q: What's the difference between a Layer 2 and Layer 3 broadcast?
A: Layer 2: hardware broadcasts.  Dest MAC address ff:ff:ff:ff:ff:ff
Layer 3: ip broadcast.  eg class C Dest IP 192.168.1.255, or 255.255.255.255

Q: What's a short description of ipv4 multicast?
A: If configured, enables multiple recipients to receive messages,  without flooding the messages to all hosts on a broadcast domain, by sending messages or data to IP multicast group addresses. Unlike with broadcasts, which aren’t forwarded, routers then forward copies of the packet out to every interface that has hosts subscribed to that group address.
Range of multicast addresses starts with 224.0.0.0 and goes through 239.255.255.255.  (class D!)

Q: What is ICMP?
A: ICMP is a management protocol and messaging service provider for IP.  Notifies hosts of network problems.  Internet Control Message Protocol.

Q: What is the difference between broadcast, unicast, and multicast?
A: A broadcast is to all devices in a subnet, a unicast is to one device, and a multicast is to some but not all devices.

Q: What RFC defined private addresses?
A: RFC 1918  -  TiPPeD oFF - and end of WW1

Q: What are the advantages of subnetting?
A: reduced network traffic
optimized performance
simplified management
facilitate spanning of large geo areas

Q: What is the mask, # of networks, hosts, and block size for a /27? assume class C
A: Subnet: /27
Mask: 255.255.255.224
Networks: 8
Hosts: 30
Block size: 32

Q: What are the 4 Cisco-recommended steps for checking IP addressing, and what does a success/fail at each step mean?
A: 1. ping 127.0.0.1. This is the diagnostic, or loopback, address.  Success: your IP stack is considered initialized. Fails: IP stack fail and reinstall TCP/IP
2. ping the IP address of the local host (and check the IP configuration too!). Success: IP protocol stack on the host can communicate to the NIC via the LAN driver.  Fails: problem with the connection to NIC
3. ping default gateway
4. ping remote server
use ping, traceroute

Q: What command returns the following?
Router# ...
Global values:
  Internet Protocol routing is enabled
FastEthernet0/0 is up, line protocol is up
  Internet address is 1.1.1.254/8
FastEthernet0/1 is up, line protocol is up
  Internet address is 2.2.2.254/8
Vlan1 is administratively down, line protocol is down
A: Router#show protocols

Q: A packet arrives at a router, and the router needs to determine where it should go.  What are Cisco's 3 packet-forwarding techniques?
A: Process Switching - regular lookup.  CPU involved every time.
Fast Switching - cache stores the most recently used destinations so that lookups are not required for every packet.
Cisco Express Forwarding (CEF) - default method on the latest routers.  CEF makes many tables and is change triggered with topology changes.  CPU proactively populates the FIB (Forwarding Information Base) with layer 3 routing it learns from the routing table, and Adjacency Table with info about how to construct the layer 2 header for a next hop IP address.

Q: What are the default administrative distances for EIGRP, OSPF, external EIGRP, Connected interfaces, Unknown (never used), Static, and RIP?
A: Connected interface: 0
Static route: 1
EIGRP: 90
OSPF: 110
RIP: 120
External EIGRP: 170
Unknown: 255 (never used)

Q: What is the main difference between RIP v1 and v2?
A: RIP version 1 uses only classful routing - all devices in the network must use the same subnet mask. RIP version 1 doesn’t send updates with subnet mask information.
RIP version 2 provides something called prefix routing and does send subnet mask information with its route updates. This is called classless routing.

Q: 6. When creating a static or default route, you can use either the [...] or the [...].
A: next-hop IP address; exit interface

Q: Crossover vs straight cables: when to use them?
A: A typical network connection is PC -> Switch -> Router. These are all straight through connections.
Anything else would be a crossover - PC -> Router, or any like devices (switch -> switch, PC -> PC, router -> router, etc).
Crossover = connecting like items.
Switches, hubs, bridges, repeaters - for cabling purposes are all the same.
http://www.techexams.net/forums/ccna-ccent/85762-pc-router-straight-thru-crossover.html

Q: What is an example exterior gateway protocol (EGP)?
A: Border Gateway Protocol (BGP).  Not in scope for CCNA.
EGP is a protocol for exchanging routing information between two neighbor gateway hosts (each with its own router) in a network of autonomous systems.

Q: What are the 3 steps in OSPF operation?
A: Neighbor and adjacency initialization.  Hellos sent out.
LSA flooding. share routing information
SPF tree calculation. Tree per area.

Q: What are the Hello packet frequencies for the different OSPF network types?
A: Broadcast and point-to-point networks: every 10 seconds
Non-broadcast and point-to-multipoint networks: every 30 seconds
Hello protocol is used to discover neighbors, establish adjacencies, and maintain relationships with other OSPF routers.

Q: What metric does OSPF use to calculate the path, and how does Cisco implement it?
A: Cost.  Arbitrary value, so Cisco uses (10^8)/bandwidth.
Other vendors may use other metrics to calculate a given link’s cost.

Q: An OSPF router will exchange LSA packets only with which routers?
A: Routers to which it has established adjacencies.

Q: What must match for 2 routers to be OSPF neighbors?
A: - Area ID
- Subnet mask
- Hello and Dead intervals
- MTU size (OSPF v2)
- Authentication password (Optional, but if it’s present, they must be the same)
- matching stub flags
OSPF Neighbors are routers who are in the same area who exchange hello packets, but not LSA information.

Q: What must you remember when configuring OSPF?
A: - area number
- add loopback addresses to the router, and add them as networks!
- use wildcards for networks - exact IPs for interfaces, or network wildcards

Q: What are good "show" commands for OSPF?
A: show ip ospf
_ Routing Process "ospf 300" with ID 223.255.255.254
_ Supports only single TOS(TOS0) routes
_ Supports opaque LSA
_ SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
_ Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
show ip ospf database
Corp#show ip ospf database
_            OSPF Router with ID (172.16.10.5) (Process ID 128)
                Router Link States (Area 0)
_Link ID         ADV Router      Age         Seq#       Checksum Link count
_192.168.10.1    192.168.10.1    2085        0x80000003 0x00847a 3
_223.255.255.254 223.255.255.254 931         0x80000005 0x00d453 3
...
show ip ospf interface
_FastEthernet0/0 is up, line protocol is up
_  Internet address is 192.168.10.1/24, Area 0
_  Process ID 300, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 1
_  Transmit Delay is 1 sec, State DR, Priority 1
_  Designated Router (ID) 223.255.255.254, Interface address 192.168.10.1
_  No backup designated router on this network
_  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
_...
show ip ospf neighbor
_Neighbor ID     Pri   State           Dead Time   Address         Interface
_223.255.255.254   0   FULL/  -        00:00:36    172.16.10.2     Serial0/3/0
_192.168.20.1      0   FULL/  -        00:00:35    172.16.10.6     Serial0/3/1
_10.10.10.2        1   FULL/BDR        00:00:36    10.10.10.2      Fast0/0
show ip protocols
_Routing Protocol is "ospf 128"
_  Outgoing update filter list for all interfaces is not set
_  Incoming update filter list for all interfaces is not set
_  Router ID 172.16.10.5
_  It is an autonomous system boundary router
_  Redistributing External Routes from,
_  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
_  Maximum path: 4
_  Routing for Networks:
_    10.10.10.1 0.0.0.0 area 0
_    172.16.10.1 0.0.0.0 area 0

Q: What is the admin distance of OSPF?
A: 110
EIGRP: 90, RIP: 120, direct: 0, static: 1

Q: What IPs are used for hello and DR/BDR updates in OSPF?
A: Hello packets are addressed to multicast address 224.0.0.5.
224.0.0.6 is used to send OSPF routing information to designated routers

Q: What does the below output tell you?
_Boulder>sh ip ospf neighbor
_Neighbor ID Pri State Dead Time Address Interface
_223.255.255.254   1   FULL/DR  00:00:31    10.10.10.1      FastEthernet0/0
_192.168.85.1 1        FULL/-   00:00:33    10.6.4.10       Serial0/1
A: Neighbor 223... is the DR, has ospf priority 1, and is reachable at 10.10.10.1.
Neighbor 192... has a - in the state column - there was no DR election (DR not required on a point-to-point link such as a serial connection.)

Q: What is the default OSPF interface priority?
A: 1
# int f0/0
# ip ospf priority 255  [1-255]

Q: What can you infer about the OSPF designated router from the below?
_RouterA2# show ip ospf neighbor
_Neighbor ID    Pri    State    Dead Time    Address    Interface
_192.168.45.2    2    FULL/BDR    00:00:24    10.1.0.5    FastEthernet0/0
_...
A: The default OSPF interface priority is 1, and the highest interface priority determines the designated router (DR) for a subnet. Router ID of 192.168.45.2 is currently the backup designated router (BDR) for the segment, so another router became the DR. It can be then be assumed that the DR router has an interface priority higher than 2. (The router serving the DR function is not present in the truncated sample output.)

Q: Which command shows the last method used to power cycle a router?
Show running-configuration
Show startup-configuration
Show restart
Show version
A: show version
System returned to ROM by power-on

Q: "#show ip eigrp topology" returns the following - what are the blue numbers?
_IP-EIGRP Topology Table for AS 100
_
_Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
_       r - Reply status
_
_P 10.10.1.0/24, 1 successors, FD is 28160
_         via Connected, FastEthernet0/0
_P 10.10.2.0/24, 1 successors, FD is 28160
_         via Connected, FastEthernet0/1
_P 10.10.20.0/24, 1 successors, FD is 2172416
_         via 172.16.0.2 (2172416/28160), Serial0/3/0
_         via 172.16.0.10 (2175232/30976), Serial0/3/1
A: FD/AD

Q: What are some things to check when troubleshooting EIGRP not forming adjacencies?
A: Interfaces between the devices are down.
The two routers have mismatching EIGRP autonomous system numbers.
Proper interfaces are not enabled for the EIGRP process.
An interface is configured as passive.
The K values are mismatched.
EIGRP authentication is misconfigured.
If adjacency is up, but not receiving updates, check routing:
The proper networks aren’t being advertised under the EIGRP process.
An access list is blocking the advertisements from remote networks.
Automatic summary is causing confusion in your discontiguous network.

Q: How can you check the interfaces on which the router has actually enabled EIGRP?
A: show ip eigrp interfaces

Q: How can you see a router's EIGRP neighbors?
A: show ip eigrp neighbors

Q: What are the two timers EIGRP uses?  What's the default for one of them?
A: Hello and Dead.  Hello default 5 s

Q: What protocol manages the communication of messages between EIGRP-speaking routers?
A: Reliable Transport Protocol (RTP)
on 224.0.0.10.  Tries multicast; if no response, tries unicast; 16 more attempts (reliable multicast)

Q: What are the 5 different EIGRP packet types?
A: Update, Query, Reply, Hello, ACK

Q: What critical conditions must be met for DUAL to work properly?
A: Neighbors are discovered or noted as dead within a finite time.
All transmitted messages are received correctly.
All changes and messages are processed in the order in which they’re detected.

Q: Do: an EIGRP router has one route to a destination with feasible distance 100 in the routing table.  In the topology table is a feasible successor router with feasible distance 200.  What command would get that route into the routing table as well?
A: Corp# config t
Corp(config)#router eigrp 20
Corp(config-router)#variance 2
load-balance traffic across the best route plus any route with a feasible distance of up to twice as large

Q: What does the following do?
Corp(config)#router eigrp 20
Corp(config-router)#passive-interface g0/0
A: Prevent this interface from sending or reading received Hello packets so that it will no longer form adjacencies or send or receive route information.
Note this is different from RIP, which still receives but doesn't send!

Q: What will be the reported distance to a downstream neighbor router for the 10.10.30.0 network, with the neighbor adding the cost to this neighbor to find the true FD?
    P 10.10.30.0/24, 1 successors, FD is 2297856
            via 172.16.10.2 (2297856/128256), Serial0/0
A. Four hops
B. 2297856
C. 128256
D. EIGRP doesn’t use reported distances.
A: B.  This FD will become the downstream neighbor's advertised distance (reported distance)!

Q: A route to network 10.10.10.0 goes down. How does EIGRP respond in the local routing table? (Choose two.)
A. It sends a poison reverse with a maximum hop of 16.
B. If there is a feasible successor, that is copied and placed into the routing table.
C. If a feasible successor is not found, a query will be sent to all neighbors asking for a path to network 10.10.10.0.
D. EIGRP will broadcast out all interfaces that the link to network 10.10.10.0 is down and that it is looking for a feasible successor.
A: B,C. EIGRP never broadcasts, so we can eliminate A and D as options. Feasible successors are backup routes and stored in the topology table, so that is correct, and if no feasible successor is located, the EIGRP will flood its neighbors asking for a new path to network 10.10.10.0.

Q: The remote RouterB router has a directly connected network of 10.255.255.64/27. Which two of the following EIGRP network statements could you use so this directly connected network will be advertised under the EIGRP process? (Choose two.)
A. network 10.255.255.64
B. network 10.255.255.64 0.0.0.31
C. network 10.255.255.64 0.0.0.0
D. network 10.255.255.64 0.0.0.15
A: 14 A,B.
Option A will work because the router will change the network statement to 10.0.0.0 since EIGRP uses classful addresses by default. Therefore, it isn’t technically a wrong answer, but please understand why it is correct for this question.
The 10.255.255.64/27 subnet address can be configured with wildcards just as we use with OSPF and ACLs. The /27 is a block of 32, so the wildcard in the fourth octet will be 31.
The wildcard of 0.0.0.0 is wrong because this is a network address, not a host address, and the 0.0.0.15 is wrong because that is only a block of 16 and would only work if the mask was a /28.

Q: Do: set up a switch so that only mac aa.bb.cc.dd.ee.ff can connect to f0/1, and all other incoming packets are dropped.
A: _Switch(config)#int f0/1
_Switch(config-if)#switchport mode access
_Switch(config-if)#switchport port-security
_Switch(config-if)#switchport port-security violation restrict
_Switch(config-if)#switchport port-security mac-address aa.bb.cc.dd.ee.ff
_
_Restrict is the same as protect, with the addition of the alerts.  P < R

Q: What are the default modes for a switch port configured with port security?
A: Max 1, violation shutdown

Q: What command generated the following MAC table entry in the switch?
vlan   mac      type    ports
1    aaaa.bbbb.0ccc STATIC      Fa0/7
A: mac address-table static aaaa.bbbb.cccc vlan 1 int fa0/7

Q: Switch and mac addresses
A: Since the MAC address is not present in the table, it will send the frame out of all ports in the same VLAN with the exception of the port on which it was received.

Q: Which switch port violation modes will alert you via SNMP that a violation has occurred on a port?
A: Shutdown and restrict mode will alert you via SNMP that a violation has occurred on a port.   Protect < Restrict (alphabetically).

Q: What is a "flat network" ?
A: A single broadcast domain.

Q: What do switches do with VLAN info when sending frames out access ports?
A: switches remove any VLAN information from the frame before it’s forwarded out to an access-link device.

Q: A frame is sent from VLAN 10 out of trunk port f0/1.  f0/1 has VLAN 10 as the default port VLAN ID (PVID), aka native VLAN. How is the frame affected?  Also, what happens to inbound traffic on f0/1?
A frame is sent from VLAN 10 out trunk port f0/2.    f0/2 has VLAN 1 as the native VLAN.  How is the frame affected?
A: Sent untagged on f0/1.  Untagged is assumed to be VLAN 10.
Tagged when sent on f0/2.

Q: What is the basic purpose of ISL and 802.1q frame-tagging?
A: The basic purpose of ISL and 802.1q frame-tagging methods is to provide inter-switch VLAN communication. Remember that any ISL or 802.1q frame tagging is removed if a frame is forwarded out an access link—tagging is used internally and across trunk links only!

Q: What are the two methods to allow for communication between VLANs?
A: Router-on-a-stick
Inter VLAN routing with an L3 switch (IVR, switch configured with a switched virtual interface (SVI))

Q: You have an L3 switch.  VLANs 10 and 20 are already set up and ports assigned.  Configure inter-vlan routing on this switch.  Make whatever assumptions are needed.
A: SW(config)#ip routing
SW(config)#int vlan 10
SW(config-if)#ip address 192.168.10.254 255.255.255.0
SW(config-if)#exit
SW(config)#int vlan 20
SW(config-if)#ip address 192.168.20.254 255.255.255.0
SW(config-if)#exit

Q: What are the different switchport modes for DTP (dynamic trunking protocol)?
A: switchport mode ...
access - no trunk
dynamic auto - can trunk, passive, waits for "trunk" or "desirable" on other end
dynamic desirable - actively try to trunk
trunk - trunk it!
nonegotiate - don't generate DTP frames   ... note this is "switchport nonegotiate"

Q: If you have a switch that provides both ISL and 802.1q frame tagging, what command under the trunk interface will make the trunk use 802.1q?
A: switchport trunk encapsulation dot1q

Q: What happens if an 802.1q-encapsulated frame is forwarded out an access link?
A: The 802.1q encapsulation is removed from the frame if the frame is forwarded out an access link.

Q: How does IEEE 802.1q work?
A: It inserts a field into the frame to identify the VLAN.  Part of that field is the 12-bit VLAN ID identifying the VLAN.

Q: How many VLANs can IEEE 802.1q support?
A: Frame inserts 12-bit VLAN ID field, 2^12 VLAN IDs = 4096, but 2 of those are reserved (all traffic destined for 4095 is discarded, and 0 is user priority data), so this can hold 4094 .

Q: Given the below, what can you say about f0/15-18?
A: They're trunk ports, they're not part of any VLAN.

Q: Identify the items in the following:
A: CO = central office

Q: WAN connection bandwidth
A: Digital Signal 0 (DS0) 64 Kbps, equivalent to one channel (1 voice/data line). Europe E0, Japan J0 equivalent.
T1 aka DS1, = 24 DS0, 1.544 Mb.    NeaR
E1 European equiv. of T1, = 32 DS0, 2.048 Mbps.    MaN
T3 aka DS3, 28 T1s = 44.7 Mbps.    Enough
E3 = 34.4 Mbps
OC-3 Optical Carrier (OC)-3 uses fiber, 3 DS3s.
OC-12 4*OC-3
OC-48 4*OC-12

Q: What are some Link Control Protocol (LCP) PPP encapsulation options?
A: Authentication
Compression
Error detection
Multilink - makes several separate physical paths appear to be one logical path at layer 3
PPP callback - call back after successful authentication

Q: A router's PPP link is set up ... you can ping, but it doesn't work.  The routing table is as shown.  What's going on?
[output cut]
  10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C       10.2.1.2/32 is directly connected, Serial0/0
C       10.0.1.0/24 is directly connected, Serial0/0
A: PPP determines and places the neighbor’s IP address in the routing table as a con- nected interface, which then allows you to ping it even though it’s actually configured on a separate IP subnet.
These IPs are bad, misconfiguration.

Q: What does VPN allow?
A: The creation of private networks across the Internet, enabling privacy and tunneling of non-TCP/IP protocols.
A VPN actually makes your local host part of the remote network by using the WAN link that connects you to the remote LAN, and will make your host appear as though it’s actually local on the remote network.
"Take my host and make it appear local to the remote resources."

Q: What are the main benefits of VPN?
A: Security: can use encryption/auth.  eg IPsec and SSL
Cost Savings: cheaper than traditional point-to-point lines
Scalability: quickly bring up new offices/mobile users
Compatibility with broadband: can use VPN over any net

Q: What are the three categories of VPN?
A: Remote access VPN: remote users can connect
Site-to-site/intranet VPNs: company's remote sites can connect
Extranet VPNs: org's partners can connect in limited way for B2B

Q: What ways can you create VPN?
A: - use IPsec to create authentication and encryption services between endpoints on an IP network
- via tunneling protocols, (eg GRE, Generic Routing Encapsulation) to establish a tunnel between endpoints on a network. The tunnel itself encapsulates other data or protocols

Q: What are common tunnelling protocols?
A: Layer 2 Forwarding (L2F).  Cisco-proprietary, first created for dial-ups (VPDNs virt private dialup).
Point-to-Point Tunneling Protocol (PPTP), from Microsoft
Layer 2 Tunneling Protocol (L2TP), by Cisco and MS to replace L2F and PPTP
Generic Routing Encapsulation (GRE).  Cisco-proprietary.  Forms virtual point-to-point links, allowing for a variety of protocols to be encapsulated in IP tunnels

Q: What is IPsec?
A: An industry-wide standard framework of protocols and algorithms for secure data transmission over an IP-based network.
Functions at the layer 3 Network layer of the OSI model.
Can only be used to encrypt IP traffic (have to create GRE tunnel for non-IP traffic, and then use IPsec to encrypt that tunnel!)

Q: What is an IPsec transform?
A: An IPSec transform specifies a single IPSec security protocol (either AH or ESP) with its corresponding security algorithms and mode.
Example transforms include the following: The AH protocol with the HMAC with MD5 authentication algorithm in tunnel mode is used for authentication.

Q: What are the primary security protocols used by IPsec?
A: Authentication Header (AH) and Encapsulating Security Payload (ESP)

Q: What does IPSec's Authentication Header (AH) protocol do?
A: provides authentication for the data and the IP header of a packet using a one-way hash for packet authentication. The sender generates a one-way hash; then the receiver generates the same one-way hash. If the packet has changed in any way, it won’t be authenticated and will be dropped. AH doesn't encrypt.

Q: What does IPSec's Encapsulating Security Payload (ESP) protocol do?
A: Provides an integrity check on the data of a packet.  Provide confidentiality, data origin authentication, connectionless integrity, anti-replay service, and limited traffic-flow confidentiality by defeating traffic flow analysis.
ADACT
auth
data int
anti replay
confid
traffic flow

Q: What are the components of IPSec's Encapsulating Security Payload (ESP) protocol?
A: Confidentiality (encryption) - sender encrypts data through symmetric algorithms.  Must be same on both endpoints of VPN.
Data integrity - receiver verifies data not altered, using checksums
Authentication - receiver auths and guarantees the source
Anti-replay service - receiver checks the sequence number (in case hacker steals a copy of it and later transmits it, duplicates can disrupt service)
Traffic flow - traffic flow confidentiality, mask the true source-destination patterns
ADACT

Q: What kinds of encryption algorithms does IPSec use, and what are some examples?
A: Symmetric encryption - requires a shared secret to encrypt and decrypt, same key used for both.  Data Encryption Standard (DES), Triple DES (3DES), and Advanced Encryption Standard (AES).
Asymmetric encryption - use different keys for encryption and decryption (private and public keys).  Rivest, Shamir, and Adleman (RSA).

Q: What are the parts of a GRE header?
A: A GRE tunnel interface supports a header for each of the following:
- A passenger protocol or encapsulated protocols like IP or IPv6, which is the protocol being encapsulated by GRE
- GRE encapsulation protocol
- A Transport delivery protocol, typically IP

Q: What are the characteristics of GRE tunnels?
A: GRE uses a protocol-type field in the GRE header so any layer 3 protocol can be used through the tunnel.
GRE is stateless and has no flow control.
GRE offers no security.
GRE creates additional overhead for tunneled packets—at least 24 bytes.

Q: Do: Configure a GRE tunnel on a router, making whatever assumptions you need.
A: Summary: make the tunnel, give it an address, specify source and dest and mode, and do the other side as well!!
# R3(config)#int tunnel 0
# %LINK-5-CHANGED: Interface Tunnel0, changed state to up
# R3(config-if)#ip address 192.168.30.2 255.255.255.0
# R3(config-if)#tunnel source f0/0
# R3(config-if)#tunnel destination 10.0.0.1
# %LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to up
# R3(config-if)#tunnel mode gre ip
# R3(config-if)#exit
# R3(config)#ip route 192.168.10.0 255.255.255.0 192.168.30.1   ! to the other end of the tunnel!
# R3(config)#exit

Q: Fibre-optic has single-mode and multi-mode.  What's the difference?
A: Red light comes in at less of an angle, and so doesn't bounce as much as green light (note more bouncing = more distance, can slow down travel and result in multimode delay distortion!)
Multimode: core has diameter large enough to allow light to enter at different angles.  Cheaper to produce, can have multimode delay distortion.
Single mode: core diameter is so small that light can only enter at one angle - light can travel further!  Tighter tolerances, more expensive.

Q: What are different network types?
A: LAN - local area network - in single building.  Client connected with cat6 via RJ45 connection, then wires go to centralized point to switch.  LAN is high speed.
WAN - wide area network - geographically dispersed.  Speeds vary, typically less than LAN speeds.
MAN - metropolitan area network - connects networks in a city.  Very high speed, redundant.  Probably single-mode fibre optic.  Use Dense Wavelength Division Multiplexing (DWDM) - different wavelengths (lambda) for different customers.
PAN - personal area network - very small (eg bluetooth).  Interconnects 2 devices over limited distance.
CAN - campus area network - connects business campus (eg cisco campus).  High speed, nearby, fibre optic multimode.
Can Lan Man Pan Wan??  CLAMP-W

Q: What is the difference between logical and physical topology?
A: logical topology - describes traffic flow in a network
physical topology - describes how things actually connect

Q: What are common network topologies?
A: Ring - token passed around (logically a ring), physically is like a star with a MAU (Media access unit).  Hosts takes turns.
Bus - main line passes through building, hosts tap into the main line.  Hosts transmit when thinks it's clear (can collide, results in corruption; CSMA/CD).  speed 10 mbps
Star - most common.  Hosts connect to ethernet switch.  Central device is SPOF
Hub and spoke - single main point, radiate out.  spoke-to-spoke traffic goes through hub
Full mesh - join all.  Optimal routing, expensive
Partial mesh - join some

Q: What are some different network architectures?
A: Client-server: clients share resources on server (running network operating system)
Peer-to-peer: clients share their own resources, host OS not as robust as network OS but good enough

Q: OSI physical - Here's data flowing over a wire - note that 1's are given at +/-5 volts.  What is this type of data flow called, and why did it go from + to -?
A: Current State Modulation - values determined by presence or absence of voltage.
Alternates + and - for AMI - "alternate mark inversion" - aims for average voltage at 0.

Q: OSI physical - here is data flowing.  What is this type of physical data flow called?
A: State Transition Modulation - a change indicates a 1!

Q: What are different types of switching that can happen at layer 3?
A: packet switching - data divided into packets (source and destination address, router makes decision)
circuit switching - temporary circuit
message switching - stream broken into messages which can be stored and forwarded

Q: What is TCP Slow Start?
A: TCP reduces its window size if a segment gets dropped.  (receiver only ACKs part of what was sent).

Q: When sending a segment, the source port is filled in with what value, and what is it called?
A: Value 1024 or higher, called Ephemeral port.
Port numbers 1023 and lower are called well-known ports.

Q: What port does SFTP use? (secure FTP)
A: 22, same as SSH

Q: What port does SCP use? (secure copy)
A: 22, same as SSH.

Q: What port does RSH (remote shell) use?
A: 514
LighTeR - use RSH with the LIGHTER to light it on fire.
HARSH LighTeR

Q: What uses port 514?
A: RSH
LighTeR

Q: What are the yellow box names?
A: Perimeter (premises) router
Firewall
DMZ

Q: What are some security threats you can mitigate with ACLs?
A: IP address spoofing, inbound/outbound
Denial of service (DoS) TCP SYN attacks
DoS TCP SYN attacks, using TCP Intercept
DoS smurf attacks
Denying/filtering ICMP messages, inbound/outbound
Denying/Filtering Traceroute
SYN flood - syns not ack'd!
SYN Flood. The attacker (Mallory) sends several packets but does not send the "ACK" back to the server. The connections are hence half-opened and consuming server resources. Alice, a legitimate user, tries to connect but the server refuses to open a connection resulting in a denial of service.

Q: What are some good rules to follow when configuring ACLs from the Internet to your production network?
A: Deny any source addresses from your internal networks.
Deny any local host addresses (127.0.0.0/8).
Deny any reserved private addresses (RFC 1918).
Deny any addresses in the IP multicast address range (224.0.0.0/4).

Q: Do: create a standard named access list called MyList that allows 172.16.128.0/19, then denies 172.16.48.0/20, and permits the rest.  Then use that on f0/0 (outbound).
A: R3#config t
R3(config)#ip access-list standard MyList
R3(config-std-nacl)#permit 172.16.128.0 0.0.31.255
R3(config-std-nacl)#deny 172.16.48.0 0.0.15.255
R3(config-std-nacl)#permit any
R3(config-std-nacl)#exit
R3(config)#int f0/0
R3(config-if)#ip access-group MyList out
R3(config-if)#exit
R3(config)#exit

Q: What are the number ranges for standard and extended ACLs?
A: Standard: 1–99 and 1300–1999.
Extended: 100–199 and 2000–2699.
lower range for each: 100, upper is 700.  Contiguous (standard then extended).  1 (for 100), then 1300 (for 700).

Q: What two tools can help notify and prevent DoS attacks?
A: IDS, IPS (intrusion detection system, prevention system)

Q: Do: What command would you use to set an access list on a VTY line?
A: line vty 0 4
access-class 110 in

Q: For the wiring "10Base5" - what do the different parts of that name mean?
A: 10 means megabits per second; base = baseband (signal takes up all the freqs on the medium, vs broadband)
5 refers to distance limitation - 5=500 meters
10Base2 - thinnet, cheapernet.  2 = 185 meters (~ 200 m)

Q: A MAC address is 48 bits.  The first 24 bits are the OUI (org unique ID).  What is another name for the OUI?
A: Vendor Code

Q: What's another name for a Mac address table?
A: CAM table (content-addressable memory)

Q: Can we have multiple mac addresses on a single port in a mac address table?
A: yes - multiple computers could connect to a single port (plug in one, then another), or port could lead to another switch/hub with many hosts.

Q: How many frames are allowed to be on one shared segment at a time?
A: Only one.

Q: What is Jamming?
A: continuing transmission of a frame that has collided, in an effort to allow all devices on the shared segment to detect the collision.

Q: If a port is in full-duplex mode, does it use CSMA/CD?
A: No, it disables CSMA/CD on the port

Q: What's a broadcast frame's destination MAC address?
A: FFFF.FFFF.FFFF.  Note that no device has that MAC, and so a switch will always flood frames with that dest. out all ports.

Q: Why does a layer 2 broadcast get flooded out all ports on a switch?
A: No device has that MAC, so a switch never learns that MAC address.  Therefore, a switch will always flood frames with that dest. out all ports.

Q: What are the Frame forwarding options?
A: cut-through switching - fast. As soon as the switch sees the first 6 bytes, it knows the dest, and can start to forward.  Might send an invalid frame accidentally!  Can check other fields as well, eg to check ACLs or QoS.
store-and-forward - waits until it sees the entire frame, calcs an FCS and checks it, then only forwards valid frames.  Saves bandwidth but takes time.
fragment-free switching - compromise. Most collisions occur within the first 64 bytes.  Looks 64 bytes into the frame only, and if a collision hasn't occurred, is forwarded. 64=SuRe!

Q: An ARP is sent from a host A.  What is in the source and dest MAC addresses of the ARP?
A: source: A's MAC address; dest: ffff.ffff.ffff

Q: What are the Cisco switch LEDs for the 2960?
A: System LED
Redundant Power Supply (RPS)
Port Status
Bandwidth Utilization
Duplex mode
SyRuP BaD - pouring SyRuP on the switch - BAD!

Q: What are the LED colors for the Cisco switch LEDs?
A: SyRuP BaD
System LED: off, amber = malfunction, green = ok
Redundant Power Supply: off = not installed/powered up, amber = malfunction, flashing amber = current power is down and RPS is going, green = ok, flashing green = RPS is powering another device at the moment
Port Status: off = no link, amber = disabled (admin/security viol), solid green = no activity, flashing green = activity, alternate green/amber = errors occurring
Bandwidth utilization: imagine this as a bargraph.  amber = max backplane utilization, green = current backplane ut.
Duplex: off = half-dup, green = full dup

Q: Troubleshooting: shove mac address aaaa.bbbb.cccc into a switch's CAM table, make whatever assumptions you need.
A: SW(config)#mac-address-table static aaaa.bbbb.cccc vlan 1 int f0/1

Q: You create some vlans.  Where is that information stored?
A: VLAN configuration is stored in flash.  Show flash, stored in vlan.dat.  Also need to "delete flash:vlan.dat" to delete them from the switch!

Q: What are the switchport modes for DTP?
A: DTP = dynamic trunking protocol.
trunk: forces port to be a trunk
dynamic desirable: initiates trunk negotiation
dynamic auto: passively waits for trunk negotiation
nonegotiate: doesn't negotiate, doesn't send DTP frames

Q: Do: config f0/1 to be a trunk with dot1q encap, and have it initiate DTP negotiation
A: # int f0/1
# switchport mode trunk
# switchport trunk encapsulation dot1q
# switchport mode dynamic desirable

Q: What tool do you use to simplify VLAN creation/management?
A: VTP (virtual trunking protocol)

Q: You can't turn VTP "off" on a switch.  What's the closest you can get?
A: Set it in "transparent" mode:
- doesn't update its database based on received advertisements
- forwards received VTP messages
- doesn't originate VTP messages

Q: What is needed for two switches to exchange VTP info?
A: VTP domain
trunk links
passwords have to match (if set)

Q: VTP propagates VLAN info, and trunks carry the VLAN traffic.  How can you save traffic?
eg, note Switch 3 receives the broadcast on vlan 2, even though it only has vlan 3 and 4.
A: # vtp pruning

Q: You're working on a switch that's not connected to prod, adding/removing VLANs etc.  You plug it into prod and take down the whole network.  Why, and how could it have been avoided?
A: VTP revision number was higher on the switch due to all the adds and deletes, so when plugged in it overwrote everything on all other switches.  Setting the VTP mode to client is no good - it will still advertise!
Solution: on the other switch, set VTP mode to transparent, then set to server mode, which resets the rev # to 0!  You could also do "#delete flash:vlan.dat"

Q: What is an ACL that allows any host to respond to a ping from any other host?
A: # access-list 102 permit icmp any any echo-reply
(there is also echo for outbound echos)

Q: What command gave the following output?  What does the "a" mean?
A: #show interfaces status
"a" means auto-negotiated.

Q: If you set one port of a network segment to "duplex full", and the other side to "duplex auto", what happens?
A: May (will?) end up with duplex mismatch - the duplex full side won't negotiate with the auto side, and the auto side could "fail downwards" to a half-duplex connection, resulting in errors.

Q: How can you see what errors have happened on a switch port?
A: Switch#show interfaces f0/1
FastEthernet0/1 is down, line protocol is down (disabled)
  Hardware is Lance, address is 00e0.f929.1001 (bia
...
_     956 packets input, 193351 bytes, 0 no buffer
_     Received 956 broadcasts, 0 runts, 0 giants, 0 throttles
_     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
_     0 watchdog, 0 multicast, 0 pause input
_     0 input packets with dribble condition detected
_     2357 packets output, 263570 bytes, 0 underruns
_     0 output errors, 0 collisions, 10 interface resets
_     0 babbles, 0 late collision, 0 deferred
_     0 lost carrier, 0 no carrier
_     0 output buffer failures, 0 output buffers swapped out

Q: If one side of your switches has high CRC errors, and the other has high late collision errors (as shown by "show int fxx"), what does this indicate?
A: Duplex mismatch.
To clear counters, type "clear counters"

Q: Port f0/1 is part of vlan 10.  You then "no vlan 10" and delete that vlan.  What happens to port f0/1?
A: Not part of any vlan.  You should assign ports to another vlan when deleting a vlan.

Q: What is a Late Collision?
A: When a collision is detected by a station after it has sent the 512th bit of its frame, it is counted as a late collision.
To allow collision detection to work properly, the period in which collisions are detected is restricted (512 bit-times). For Ethernet, this is 51.2us (microseconds), and for Fast Ethernet, 5.12us. For Ethernet stations, collisions can be detected up to 51.2 microseconds after transmission begins, or in other words up to the 512th bit of the frame.  ethernet = 10 Mbps = 10,000,000 bps.
To see the error: "show interface fx/x"

Q: A router has four routing processes running on it, and each process has received these routes:
EIGRP (internal): 192.168.32.0/26
RIP: 192.168.32.0/24
OSPF: 192.168.32.0/19
Which of these routes will be installed in the routing table?
A: Since EIGRP internal routes have the best administrative distance, it's tempting to assume the first one will be installed. However, since each of these routes has a different prefix length (subnet mask), they're considered different destinations, and they will all be installed in the routing table.
If a packet arrives on a router interface destined for 192.168.32.1, which route would the router choose? It depends on the prefix length, or the number of bits set in the subnet mask. Longer prefixes are always preferred over shorter ones when forwarding a packet.

Q: A host has IP 169.254.31.31.  Is this routable?
A: No, this is the APIPA, and the host assigned it to itself.
APIPA 169.254.0.0 - 255.255 is APIPA.

Q: Broadcast vs directed broadcast - what's the difference?
A: Broadcast: 255.255.255.255
Directed: 192.168.1.255  <-- specifies the network

Q: What is CIDR also called?
A: Classless Inter-Domain Routing, sometimes called supernetting

Q: What are some of the benefits of ipv6?
A: - increased address space
- simplified header (ipv4: 12 fields, v6: 5 fields)
- no broadcasts
- security and mobility features built-in
- no fragmentation: MTU discovery is performed for each session
- can coexist with ipv4 during migration (dual stack)

What are some IPv6 address types?

Q: In IPv6, what is a Rendezvous Point?
A: A router which forwards multicast traffic to routers asking to receive the traffic.  A flag is set in the Flags portion of a multicast address

Q: In ipv6, what is Link Local scope?
A: Basically, it's the same subnet.  Eg, FF02::1 = a multicast to all the nodes in the link-local scope

Q: What is FF02::1, and FF02::2?
A: FF02::1 - all the nodes in the link-local scope - like an ipv4 broadcast.
FF02::2 - all the routers in the link-local scope
Note FF00::/8 = multicast
Multicast address starts with 1111,1111,flags,scope,group ID ... the scope of "2" means link-local scope.  11111111 = FF, which is multicast.

Q: Give some notes about Link Local Address, including how it's formed
A: - FE80::/10
- 1111 1110 01, followed by 54 zeros, then the interface ID (can use EUI-64 address)
- not routable, but can communicate on the network segment - eg for autoconfig or neighbor discovery
- replacement for APIPA
- InterfaceID can be automatically or statically assigned
when you give an interface an ipv6 address, it also gets a link local address

Q: What are some points about Unique Local ipv6 addresses?
A: Starts with FC00::7, can't be routed over public net, but can be privately.

Q: When is the ipv6 Unspecified Address used?
A: Unspecified address is "::" ... all zeroes!  Used as the source address when sending:
- Neighbor Solicitation messages
- Router Solicitation messages

Q: For every ipv6 unicast address added to an interface, what group must the host join?
A: A host is required to join a Solicited-Node multicast group for each of its configured unicast or anycast addresses.
Example: If we have an interface with the IP address fe80::2aa:ff:fe28:9c5a the associated Solicited-Node multicast address is ff02::1:ff28:9c5a. So we must join to the multicast group represented by this address.

Q: What is the layout of a Solicited Node Multicast Address?
A: First 104 bits: FF02::1:FF
- FF means multicast
- 02 means "link local scope"
- ::1:FF means "solicited node multicast group"
Last 24 bits: last 24 bits of the ipv6 unicast address

Q: What are uses of a Solicited Node Multicast Address?
A: used instead of ipv4 ARP broadcast - eg, host knows ip of its router, to get its mac it can send a multicast to the router's Solicited Node M. Address
used for Duplicate Address Detection

Q: What are the two approaches for ipv6 autoconfiguration?
A: Stateful - use DHCPv6 server
Stateless - use ipv6 router

Q: What message is sent in ipv6 DHCPv6?
A: Solicit, Advertise, Request, Reply - SARR
Client sends Solicit message from link local address (eg FE80::A) to FF02::1:2 (multicast link local, means "All DHCP servers and relay agents on the local network segment").
Server sends back Advertise message (source = FE80::B, dest = FE80::A)
Client sends Request
Server sends Reply

Q: What are the steps for ipv6 stateless autoconfiguration?
A: First, node connects and sends solicitation with its own address to ensure that nobody else has its link local address.  No response = good.
If router hasn't advertised itself yet, node sends Router Solicitation (source = ::, dest = FF02::2, all routers on the link, ICMP 133)
Router responds with RA (source = router's LL address, dest = FF02::1, all nodes on link, ICMP 134)

Q: Here is a syslog line.  What does it mean?
A: 000021: sequence number.  Requires config service "#service sequence-numbers"
timestamp:  Requires config service "#service timestamps log [datetime | log]"
facility: facility to which the log message refers
sev level
mnemonic: abbrev description
full description

Q: What are the main parts of SNMP?
A: SNMP manager, agent, MIB (management information base). mgr can query, agent can send trap notification.

Q: You want to be notified when a router's interface goes down.  What can you do?
A: Set up syslog and SNMP.
Syslog: router can send a syslog message eg when an interface goes down.  Use syslog server (eg, kiwi syslog server)
_#logging 1.1.1.1
_#logging trap notifications
Can also set up an SNMP server:
_! set community strings
_#snmp-server community CCENT ro
_#snmp-server community CCNA rw
_! information about the device
_#snmp-server location Richmond KY
_#snmp-server contact Kevin W
_! Set the host
_#snmp-server host 192.168.1.1 version 2c CCNA
_#snmp-server enable traps all

Q: You've VTY'd into a router, but can't see any syslog messages.  What do you need to do?
A: #terminal monitor
show console messages even if connected via vty line

Q: Do: configure a router to send SNMP
A: ! set community strings
#snmp-server community CCENT ro
#snmp-server community CCNA rw
! information about the device
#snmp-server location Richmond KY
#snmp-server contact Kevin W
Router has now been configured to respond to queries. Set up router to send notifications if something happens
! Set the host
#snmp-server host 192.168.1.1 version 2c CCNA   ! using that community
#snmp-server enable traps all
To see what traps have been enabled, do "show run | i traps"
Can disable individual traps with "no snmp-server enable traps xxx xxxxx"

Q: In netflow, what is a flow?
A: A unidirectional flow of packets

Q: What are the benefits of NetFlow?
A: - see who are top users in the network
- accounting
- security (check DoS attacks, eg)
- network planning
- check quality of service (paths being delayed, dropped?)

Q: What are the criteria for packets to be considered in the same flow?
A: same source IP
same destination IP
same source port number  (e.g., multiple browser tabs would have different source ports)
same destination port number
same layer 3 protocol type (eg all IP)
same Type of Service (ToS) value (in the IPv4 header is a ToS byte, )
same ingress interface

Q: What is IP Precedence Value?
A: QoS marking that uses the three leftmost bits of the ToS Byte (ipv4 header)

Q: What is Differentiated Service Code Point (DSCP)?
A: QoS marking that uses the six leftmost bits of the Type of Service Byte (ipv4 header)

Q: What is the difference between IP Precedence Value and Differentiated Service Code Point (DSCP)?
A: IP Precedence Value - QoS marking that uses the three leftmost bits of the ToS Byte (ipv4 header)
Differentiated Service Code Point (DSCP) - QoS marking that uses the six leftmost bits of the Type of Service Byte (ipv4 header)

Q: Do: you want to monitor network traffic on a router's interface.  Set something up for that, make whatever assumptions you need!
A: R2(config)#int fa0/0
R2(config-if)#ip flow ingress
R2(config-if)#ip flow egress
(Note flow is unidirectional, so have to do both of them)
See the info on the router:
#show ip cache flow
... returns a bunch of data
Export it to somewhere:
R2(config)#ip flow-export source lo0
R2(config)#ip flow-export version 5  !check docs
R2(config)#ip flow-export destination 192.168.1.50 9996  !check docs

Q: How does MPLS differentiate traffic?
A: Multiprotocol Label Switching
assign labels to packets, and routers within the MPLS cloud can route based on the labels
MPLS inserts a 32-bit shim header in between layer 2 and layer 3
routers in the MPLS cloud use the packets to make decisions

Q: What are the different parts of the MPLS cloud below?
A: CPE - cust premise equipment
ELSR - edge label switch router (injects shim header)
LSR - label switch router (every LSR hop changes the label)

What are the below terms in this ISDN circuit?

Q: What is ISDN?
A: Integrated Services Digital Network - digital circuit tech, where circuit is divided into logical B channel (voice, data, video) and D channels (signalling channel, carries protocols to set up/maintain/tear down)
B = bearer channel (carrying the traffic, can send voice or video or data)
D = delta or data or D channel

Q: What are the signalling protocols used on ISDN's D channel?
A: q.921 - ISDN's layer 2 signalling protocol  (PaNT 921 = 2)
q.931 - ISDN's layer 3 signalling protocol  (931 = 3)

Q: What are the two types of ISDN circuits?
A: BRI and PRI
BRI - Basic Rate Interface - 2 B channels (64 kbps) and one D channel (16 kbps)
PRI - Primary Rate Interface - based on T1 (23 B channels and one 64 kbps D channel); or E1 (30 B channels and one D channel).
T1 - 24 channels (1 D, 23 B)
E1 - 32 channels (1st channel reserved for framing and sync, 17th channel is D, 2-16 and 18-32 are B)

Q: When would you use ISDN?
A: ISDN - very mature, sometimes can get ISDN circuit to a location that can't get DSL or cable modem, otherwise usually don't use it

Q: ISDN router - the back says "s/t" or "u".  What does that mean?
A: if router says "S/T", you have to plug it into an NT1
if it says "U" - then "You (U) have an NT1 in your router", so your router will take a 2-wire connection

Q: ISDN terminology:
TA (Terminal adaptor):
TE1 (Terminal endpoint 1):
TE2 (Terminal Endpoint 2):
NT1 (network termination 1):
R Reference point:
S/T reference point:
U Reference point:
A: TA (Terminal adaptor): adapts non-ISDN device to ISDN network
TE1 (Terminal endpoint 1): device that natively supports ISDN
TE2, Terminal Endpoint 2: a non-ISDN device
NT1 (network termination 1): converts between a 2-wire ISDN circuit and a 4-wire ISDN circuit
R Reference point: sits between TA (terminal adaptor) and non-ISDN device (TE2, Terminal Endpoint 2).
S/T reference point: between an NT1 and an ISDN-speaking device
U Reference point - point between NT1 and the wall jack

Q: What is the bandwidth of T1, E1, T3, and E3?
A: bandwidth (Mbps):
T1 - 1.544
E1 - 2.048
T3 - 44.7
E3 - 34.4

Q: What is DSL?
A: Digital Subscriber Line - a collection of broadband techs (eg ADSL, SDSL, VDSL) that use a telephone line for transmission

Q: What are DSL variants?
A: variant; upload/download speeds Mbps; max distance to DSLAM ft
Asymmetric DSL (ADSL); 1.544, 8; 18000 ft
Symmetric DSL (SDSL); 1, 1; 12000 ft
Very High Bit-Rate DSL (VDSL); 12, 52; 4000 ft

Q: What is ADSL?
A: ADSL - asymmetric DSL - phone and PC use the same line - terminates on a DSLAM (DSL Access Multiplexer).  Upload/download speeds different.
connection via ATM

Q: What is ATM?
A: Asynchronous Transfer Mode - data sent in fixed-length cells (53 byte cells, 48 bytes payload, 5 bytes header)

Q: What is a DSLAM?
A: DSL Access Multiplexer

Q: What is a Load Coil?
A: a device the telephone company installs on their copper telephone wires at intervals of 18000 ft to counteract capacitance buildup

Q: Identify the parts of the below ADSL (Asymmetric DSL)
A: - connection terminates on DSLAM
- ATM = Asynchronous transfer mode
- at home: IP at layer 3, Ethernet at layer 2
- using PPPoE - Point-to-Point Protocol over Ethernet - lets you authenticate
- underlying PPPoE is ATM at layer 2
- max distance 18000 ft due to capacitance build up on the wires, which then causes a phase shift

Q: What are the different kinds of virtual circuits for Frame Relay?
A: SVC - switched virtual circuit - brought up on as-needed basis
PVC - permanent virtual circuit

Q: What is the difference between Point-to-Point, and Point-to-Multipoint?
A: Point-to-Point: single VC connecting two endpoints, where both endpoints belong to the same IP subnet
Point-to-Multipoint: a connection from one endpoint to one or more other endpoints, where all endpoints belong to the same IP subnet

Q: What is the difference between the FECN and BECN bit?
A: BECN bit: when a frame is going to the client router, the provider can mark the BECN bit in the Frame Relay frame header, telling the router to slow down its downloading.
FECN bit: the router sends a ton of data.  Setting the FECN bit ... this tells the receiver to generate and send a frame back (Q.922 test frame) to the sender which the provider will mark with a BECN bit, so the sending router can be advised it's taxing the network.

Q: Give some notes about Cable WAN
A: Cable modem - use TV cable to connect
Hybrid Fiber-Coax (HFC) distribution network - cable co's distribution network composed of fiber optic cabling and coax, which carries both TV and data
cable modem - may be sharing bandwidth with neighbors
different freqs for TV, upload/download.  Typical cable modem freqs: upstream 5 MHz - 42 MHz, downstream 50 MHz - 860 MHz (vary by carrier)

Q: What is DOCSIS?
A: Data-Over-Cable Service Interface Specification - a set of standards specifying the use of different frequency ranges in a cable TV network for Cable WAN.
(different versions used by different cable companies)

Q: What are some SSL VPN options?
A: 1. securely use a web browser (e.g. Clientless Cisco SSL VPN)
2. install client software (eg Cisco AnyConnect SSL VPN)

Q: What comprises an IPSec tunnel?
A: outer tunnel is used to negotiate the config of the inner tunnel, and the inner tunnel protects data through encryption and hashing.
IKE (Internet Key Exchange) Phase I Tunnel: outer tunnel (aka an ISAKMP tunnel - Internet Security Association and Key Management Protocol) in which the security parameters for the inner tunnel are negotiated
IKE Phase II Tunnel: inner tunnel in which an IPsec connection (aka IPsec tunnel) in which traffic is protected

Q: What kind of traffic can IPsec protect?
A: IPSec can only protect unicast IP traffic (not multicast or broadcast ... you could encapsulate that within a GRE packet)

Q: What are some WAN connection protocols?
A: Metro Ethernet
VSAT
Cellular 3G/4G
MPLS
T1/E1
ISDN
DSL
Frame Relay
Cable
VPN

Q: What is Metro Ethernet, and its advantages?
A: Metro Ethernet
interconnect sites within metro area
MAN - based on ethernet, typically uses fibre optics
advantages: will easily connect with LANs; typically less expensive; typical speeds 10 Gps or 40 Gps

Q: What is VSAT?  What are its data rates, advantages and disadvantages?
A: VSAT - very small aperture terminal
Uses small satellite dishes (less than 3 meters) installed at network.  Good for remote locations or ships.
data rates 56 Kbps or 4 Mbps
data delay due to travel to satellite, sensitive to weather conditions

Q: What is Cellular 3G/4G?
A: cellular technology
"G" is referring to generation of the technology
standards defined by ITU-R (International telecommunications union, radiocomm. sector)
LTE (long-term evolution) is commonly offered as "4G", though it doesn't really meet 4G
WiMax - 802.16M
internet access to mobile or stationary devices (via tethering)

Q: What is MPLS?
A: Multiprotocol Label Switching
assign labels to packets, and routers within the MPLS cloud can route based on the labels
With labels:
- can isolate traffic, can do advanced traffic engineering
- QoS - can offer different QoS by labels
- can handle all protocols

Q: How does MPLS labelling work?
A: MPLS inserts a 32-bit shim header in between layer 2 and layer 3.  Header has label.

Q: What are the different components in an MPLS network?
A: CPE - cust premise equipment
ELSR - device at edge of MPLS cloud, adds/removes labels on entry/exit. Also known as PE (Provider Edge) router.
LSR - label switch router, relabels and forwards.  Also known as P (provider) router.  every LSR hop changes the labels

Q: What is SONET?
A: Synchronous Optical Network (SONET).  A fiber optic multiplexing standard that allows multiple channels of communication to share a fiber optic cable.

Q: What is the bandwidth for T1?
A: 1.544 Mbps
originally designed for telephones
24 channels (each channel is a DSO)
64 kbps of bandwidth per DSO
Nyquist Theorem "min sampling rate should be twice the highest frequency", so for voice, we should take 8000 samples per second (2x voice freq of 4000)
8-bit samples
T1 has one 8-bit sample per each channel, 24 channels
24 channels x 8 bits/sample + 1 framing bit = 193 bits per frame
per Nyquist, 8000 samples, or frames, per second
193 * 8000 = 1.544 Mbps of bandwidth on T1 circuit

Q: What is a SuperFrame (SF) and an Extended SuperFrame (ESF)?
A: SuperFrame: glue 12 frames together
ESF: 24 frames

Q: What layer protocol runs over a T1, E1, T3, or E3 line?
A: A layer 2 protocol, like PPP, runs over the digital circuit.

Q: What does the bandwidth command in the following do?
Router(config)# interface serial 0
Router(config-if)#  bandwidth 500
A: This command does not control the clock speed!  It's used by routing protocols like OSPF or EIGRP for metric calculations.
Per cisco: "The bandwidth command sets an informational parameter to communicate only the current bandwidth to the higher-level protocols; you cannot adjust the actual bandwidth of an interface with this command. ... This is a routing parameter only; it does not affect the physical interface."

Q: In PPP, is PAP one-way or two-way?
A: PAP is one-way, there is a server and a client.
eg, server:
R1(config)#username ROUTER2 password cisco
R1(config)#int s0/0
R1(config-if)#encapsulation ppp
R1(config-if)#ppp authentication pap
and client:
R2(config)#int s0/0
R2(config-if)#encapsulation ppp
R2(config-if)#ppp pap sent-username ROUTER2 password cisco
R2(config-if)#end

Q: What is PPP link quality management?
A: Link quality management which is a way to monitor the quality of a link in PPP. When PPP detects too many errors on a link, the link is shut down.  When the link does not meet the specified quality, PPP does not activate the link.

Q: What are the frame relay PVC statuses, and what do they mean?
A: Active - all ok
Inactive - good connection between local router and frame relay switch, but not between FR switch and the far-end router
Deleted - bad connection between local router and FR switch

Q: ATM (Asynch Transfer Mode), which is used by ADSL (asynch DSL), uses a PVC (perm virtual circuit) which is identified by what?
A: VPI/VCI pair of numbers.
VPI = virtual path identifier
VCI = virtual channel identifier

Q: What is a Smart Serial Connector?
A: a small form-factor, 26-pin connector used to connect a Cisco router to a serial device such as a CSU/DSU.

Q: "show ip route" shows codes at the start of each line.  What are the codes and meaning?  C,L,S,O,D, and what are their default administrative distances?
A: C = directly connected (0)
L = local interface (0 ?)
S = static (1)
O = ospf (110)
D = eigrp (90)

Q: What are the Control Plane and Data Plane of a router?
A: Data Plane: where the data flows
Control Plane: behind-the-scenes

Q: What are the LEDs on the front of a router?
A: Sys
Act
POE
RPS
PS

Q: What are primary things that "show version" shows?
A: - version
- uptime
- where ios image is store
- platform
- how much memory is installed (774144K/12288K => add these to get K, divide by 1024 to get Megs)
- overview of interfaces

Q: show run | xxxx
What are some values of x?
A: show run | begin x     starts at first instance of x
show run | section x   shows each section that starts with x
show run | include x    shows each line that includes x
show run      ... press "/" to start search, jumps to first instance

Q: R1#config t
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#enable secret cisco
R1(config)#exit
#show run
...
enable secret 5 $1$mERr$hx5rVt7rPNoS4wqbXKX7m0
What is the blue text?
A: MD5 (Message Digest 5) hash.  A 128-bit result of an algorithm run on a string of chars.  Technically, not an encryption.

Q: What happens as a result of the below commands on a new router?
R1(config)#int f0/0
R1(config-if)#ipv6 enable
R1(config-if)#exit
R1(config)#exit
A: f0/0 is assigned a link local address.
# show ipv6 int brief
FastEthernet0/0            [administratively down/down]
    FE80::230:A3FF:FE4C:2A01
Note that the MAC address was used to create the interface ID portion of the link local address (MAC address is 0030.a34c.2a01)
Joins the "all nodes" group:
R1#show ipv6 int f0/0
...
  Joined group address(es):
    FF02::1   -- all nodes

Q: What is the difference between a "login" banner, and an "motd" banner?
A: #banner login $ aoeu $
#banner motd $ uuuu $
You'll see the MOTD banner when you connect.  You'll only see the login banner if login is configured.
In login, say "Access is prohibited", eg.

Q: How do you get the default gateway for your computer in windows, and in OSX?
A: Windows:
ipconfig /all
OSX needs 2 commands:
$ifconfig
$ route -n get default

Q: How can you set up continuous ping in Windows and OSX?
A: Windows:
ping -t 192.168.2.24
OSX:
ping 192.168.2.24

Q: Bad network, you can't ping R4 from R1.  What's a good tool to troubleshoot?
A: Go on the router, and "traceroute" to the loopback
break out with ctrl-shift-6

Q: What are useful error stats from the router interface check below?
_R1#show int s0/1/0
_Serial0/1/0 is up, line protocol is up (connected)
_  Hardware is HD64570
_  Internet address is 10.1.1.1/30
_  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
_     reliability 255/255, txload 1/255, rxload 1/255
_  Encapsulation PPP, loopback not set, keepalive set (10 sec)
_  LCP Open
_  Open: IPCP, CDPCP
_  Last input never, output never, output hang never
_  Last clearing of "show interface" counters never
_  Input queue: 0/75/0 (size/max/drops); Total output drops: 0
_  Queueing strategy: weighted fair
_  Output queue: 0/1000/64/0 (size/max total/threshold/drops)
_     Conversations  0/0/256 (active/max active/max total)
_     Reserved Conversations 0/0 (allocated/max allocated)
_     Available Bandwidth 1158 kilobits/sec
_  5 minute input rate 0 bits/sec, 0 packets/sec
_  5 minute output rate 0 bits/sec, 0 packets/sec
_     0 packets input, 0 bytes, 0 no buffer
_     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
_     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
_     0 packets output, 0 bytes, 0 underruns
_     0 output errors, 0 collisions, 1 interface resets
_     0 output buffer failures, 0 output buffers swapped out
_     0 carrier transitions
_     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up
A: Note you might want to clear out stale data - "#clear counters"
_R1#show int s0/1/0
_Serial0/1/0 is up, line protocol is up (connected)
_  Hardware is HD64570
_  Internet address is 10.1.1.1/30
_  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
_     reliability 255/255, txload 1/255, rxload 1/255
_  Encapsulation PPP, loopback not set, keepalive set (10 sec)
_  LCP Open
_  Open: IPCP, CDPCP
_  Last input never, output never, output hang never
_  Last clearing of "show interface" counters never
_  Input queue: 0/75/0 (size/max/drops); Total output drops: 0
_  Queueing strategy: weighted fair
_  Output queue: 0 [if high, many packets waiting]/1000/64/0 [how many dropped?] (size/max total/threshold [max # of packets from top talker allowed]/drops)
_     Conversations  0/0/256 (active/max active/max total)
_     Reserved Conversations 0/0 (allocated/max allocated)
_     Available Bandwidth 1158 kilobits/sec
_  5 minute input rate 0 bits/sec, 0 packets/sec
_  5 minute output rate 0 bits/sec, 0 packets/sec
_     0 packets input, 0 bytes, 0 no buffer
_     Received 0 broadcasts, 0 runts [frame too small for medium - eg, <67 bytes for ethernet], 0 giants [> 1518 bytes], 0 throttles
_     0 input errors, 0 CRC [due to collisions], 0 frame [partial frame], 0 overrun, 0 ignored, 0 abort
_     0 packets output, 0 bytes, 0 underruns
_     0 output errors, 0 collisions, 1 interface resets
_     0 output buffer failures, 0 output buffers swapped out
_     0 carrier transitions
_     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

Q: What layer does CDP run at?
A: Layer 2.  This means that you can have bad IPs, and it will still return data.

Q: Do: tell router to get its f0/0 IP address from DHCP
A: #int f0/0
#ip address dhcp
#no shutdown
#exit
Note: you will need int f0/0 to forward the DHCP broadcast ...
#int f0/0
#ip helper-address 172.16.1.2   !DHCP server
Then "show ip int brief" shows that f0/0 got its address by method DHCP.

Q: What are some commands to show information about DHCP pools on a router?
A: # show ip dhcp pool       - shows pools
# show ip dhcp binding   - shows existing leasing

Q: Do: config NAT so that inside local IP 10.1.1.1 is sent out to the internet as 4.4.4.2
A: #int f0/0
#ip nat inside
#int f0/1
#ip nat outside
#ip nat inside source static 10.1.1.1 4.4.4.2
After pinging, you can "show ip nat translations"

Q: why do network devices need accurate time?
A: - helps admins correctly interpret logs
- using digital certs - ensure that they're only used during valid times

Q: What is NTP Stratum?
A: measures believability of a time source.  Stratum level 1 atomic clock.  Stratum level increments for each "sync hop" (eg, my router connects to an NTP atomic clock w/ stratum level 1, so my router has stratum level 2; if other devices sync from this router then they're level 3)

Q: Do: NTP configuration and verification: R1 is a router in the cloud.  Set it as the master clock, and set R2 to refer to R1, and R3 to R2.
A: R1#clock set 13:36:00 31 July 2015
R1#config t
R1(config)#clock timezone UTC 0   !hours offset from UTC
R1(config)#ntp master 5    !sets this as the master
R2#config t
R2(config)#ntp server 1.1.1.1  !R1 loopback
R2(config)#clock timezone PST -8
R2(config)#clock summer-time PDT recurring
Timezones EST
clock summer-time EDT
... wait until it syncs.
R3#show clock
09:43:25.885 ....
R3#show ntp associations
R3#show ntp status
shows the clock is sync'd, and shows its status

Q: What are commands to check NTP-related info on a router?
A: R3#show clock
09:43:25.885 ....
R3#show ntp associations
R3#show ntp status
shows the clock is sync'd, and shows its status

Q: Use telnet to show that your router can connect to port 80 on 192.168.1.1
A: >telnet 192.168.1.1 80

Q: What are some basic security threats for devices, other than hacking access?
A: Physical threats
- drop the device
- incorrect label devices
Electrical
- voltage fluctuations
- lightning
- not grounded
Employee training to ensure they handle things correctly
Malicious users
- physically securing devices
- biometric monitoring
Environmental threats
- temp, humidity
- monitoring for this

Q: Create an access list that logs any denied attempts
A: #access-list 1 permit 10.1.1.1 0.0.0.255
#access-list 1 deny any log
#line vty 0 4
#access-class 1 in
and that's logged, can send to syslog

Q: You have hundreds of devices (routers, switches, etc).  Instead of setting up usernames on each one, what should you do?
A: Use an AAA server
- authentication
- authorization
- accounting
Common AAA servers: Radius, TACACS

Q: What are the differences between Radius and TACACS?
A: Radius:
UDP
encrypts password
enhanced accounting
standard-based
TACACS:
TCP
encrypts packet
basic accounting
cisco-proprietary

Q: What's a man-in-the-middle attack?
A: Man sends gratuitous ARP to user, who then thinks that his default gateway is the man's computer.  He then forwards it and can inspect packets later.

Q: What is one way to help block a man-in-the-middle attack?
A: Shut down all the ports on the switch when you first unbox it.  Prevents a user from plugging in to an unused port and sending gratuituous ARP to update their default gateway mac address.

Q: Why would you put unused ports in an unused VLAN?  And how do you do that?
A: Prevents ppl from getting access to network if they get physical access.
#vlan 999
#name NULL_VLAN
#end
#int range fa 1/0/1-24
#switchport mode access
#switchport access vlan 999

Q: What is a VLAN hopping attack, and how can it be prevented/discouraged?
A: VLAN Hopping Attack: where an attacker's device is able to attack a device in another VLAN without crossing a router.
Attacker double-frames their packet.  Outer frame is tagged as VLAN 1, the default native VLAN, and the inner frame is tagged VLAN 20.  When the packet gets to the switch, if the switch has native VLAN 1 for the trunk, then the VLAN 1 tag gets stripped off (since it's native), and the VLAN 20 tag is exposed.  This then has access to VLAN 20, without going through any layer 3 router or filtering.
Solution:
- don't use default 1 as native VLAN
- assign an access VLAN other than VLAN 1 to every access port
- don't have any production traffic assigned to native VLAN ports

Q: What IEEE standard is STP?
A: 802.1D
Radia Perlman, working at DEC
ViSioN 1D

Q: A router receives a packet with a TTL 1.  What happens to the packet?
A: Not forwarded, TTL is decremented and now it's 0.

Q: What's a broadcast storm?
A: A broadcast frame (i.e., destined for FFFF.FFFF.FFFF) circulates endlessly, because it has no TTL field.

Q: What problems happen with a Layer 2 topological loop if STP isn't used?
A: - broadcast storm
- duplicate frames can be sent
- MAC address table corruption

Q: What is the default priority for STP?
A: 32768   (MoNKey SHaVe)

Q: When calculating SPT and finding the root port on a switch, which port is chosen if the costs are equal?
A: The lowest port ID

Q: Figure out root bridge, designated ports, and blocking ports for the below.
A: 1. figure out the root bridge (lowest bridge ID)
2. figure out root ports on each switch (lowest cost to root, tiebreaker is port ID).  Cost 10Gbps = 2, 1Gbps = 4, 100Mbps = 19, 10Mbps = 100
3. figure out designated ports on each segment (the end closest to the root)
4. rest are blocked

Q: STP convergence time: Suppose a switch has 1 blocking port and 1 forwarding port, and the link fails on the forwarding port.  How long will it take for the blocked port to become a designated port, with traditional CSTP (IEEE 802.1D)?
A: 50 seconds
Blocking: 20 s - remains here for 20 s, waiting for a BPDU
Listening: 15 s - listening to BPDUs
Learning: 15 s - starts to populate mac address table
Forwarding

Q: What are some STP variants?
A: CSTP: IEEE 802.1D - all VLANs use common STP topology (CSTP)
PVST: per-vlan spanning tree, used over ISL trunks
PVST+: per-vlan spanning tree, used over IEEE 802.1q trunks
MISTP: multiple-instance STP
MSTP: multiple spanning trees protocol (802.1s)
fast convergence (2-3 seconds)
RSTP: rapid STP (802.1w)
RPVST+ -- needs a lot of switch processing power

Q: What is an example thing that RSTP does to speed convergence time?
A: Sample change: on topology change (blocking switch becomes forwarding), switch notifies other switches via a TC (topology change) bit in the BPDU, which causes those switches to start re-learning the network topology.

Q: What does the following do?
#config t
#spanning-tree vlan 100 root primary
#spanning-tree vlan 300 root primary
#spanning-tree vlan 200 root secondary
A: Should adjust the priority for this switch and make it primary for 100 and 300, and secondary for 200.
can verify with
#show spanning-tree vlan 200

Q: You plug in a laptop into a switch.  How long may it take before traffic can flow on that port?
A: 30 seconds.  Switch may have to go through listening (15 s) and learning (15 s) on that port.
Note a regular STP blocking port takes 50 s to transition from blocking to forwarding, as it spends 20 s more in blocking before transitioning to listening and then learning.

Q: What does "R1(config-if)#spanning-tree portfast" do?
A: Tells a port to bypass listening and learning states, which are 15 s each, so the port is instantly available.
Should set up "spanning-tree bpduguard enable"

Q: How can you set up bpduguard and portfast for all non-trunk ports quickly?
A: SW(config)#spanning-tree portfast bpduguard enable
SW(config)#spanning-tree portfast default

Q: What are some Etherchannel load-balancing algorithms?
A: dst-ip (destination ip), dst-mac
src-dst-ip, src-dst-mac
src-ip, src-mac
The below pic has 4 lines, so it takes 2 bits to determine which line to go on.  As shown, if something was sent to machines with MACs ending in 1, 5, or D, all of them would go on the same line, if we were using the dst-ip as the load balance.
Note if there were 2 links, only need 1 bit to load balance; if 8 links, would need 3 bits.

Q: What must be the same for all ports for an etherchannel to be negotiated?
A: Same speed
Same duplex
Same VLAN assignment

Q: PAgP and LACP port negotiation - what results in a channel being negotiated?
A: On - On - yes
Auto-Desirable - yes
Desirable-Desirable - yes
Active-Active - yes
Active-Passive - yes
Nothing else results in negotiation!
note this is for etherchannel. eg channel-group 1 mode active

Q: You have two switches, and want to join them with a straight-through cable.  How can you make that work?
A: Use auto-MDIX (automatic medium-dependent interface crossover).  When automatic medium-dependent interface crossover (auto-MDIX) is enabled on an interface, the interface automatically detects the required cable connection type (straight through or crossover) and configures the connection appropriately.
you must also set the interface speed and duplex to auto so that the feature operates correctly.
#configure terminal
#int f0/0
#speed auto
#duplex auto
#mdix auto
#exit

Q: Show a listing of all the etherchannels created, and ports assigned to each.
A: _Switch#show etherchannel summary
_Flags:  D - down        P - in port-channel
_        I - stand-alone s - suspended
_        H - Hot-standby (LACP only)
_        R - Layer3      S - Layer2
_        U - in use      f - failed to allocate aggregator
_        u - unsuitable for bundling
_        w - waiting to be aggregated
_        d - default port
_
_
_Number of channel-groups in use: 1
_Number of aggregators:           1
_
_Group  Port-channel  Protocol    Ports
_------+-------------+-----------+----------------------------------------------
_
_1      Po1(SU)           LACP   Gig0/1(P) Gig0/2(P)

Q: Do: you have a trouble ticket, etherchannel traffic is slow.  You suspect load balancing is the issue.  What commands can you use to fix it?
A: S1#show etherchannel load-balance
EtherChannel Load-Balancing Operational State (src-mac):
Non-IP: Source MAC address
  IPv4: Source MAC address
  IPv6: Source MAC address
Only going by src-mac, so if one machine is hogging bandwidth, it will slow things down.
S1#config t
Enter configuration commands, one per line.  End with CNTL/Z.
S1(config)#port-channel load-balance src-dst-mac
S1(config)#exit

Q: What is MTU?
A: Maximum Transmission Unit - how big a packet can be when sent out an interface.

Q: What are the main differences between Distance Vector Routing Protocols and Link State Routing Protocols?
A: Distance vector routing:
- involves two factors: distance to destination, and direction
- routing information is only exchanged between directly connected neighbors, doesn't know where the neighbor got its information.  "routing by rumor."
- Measures like split horizon and poison reverse are employed to avoid routing loops.
Link-state routing:
- all routers know about the paths reachable by all other routers in the network
- link-state information is flooded throughout the link-state domain (an area in OSPF or IS-IS) to ensure all routers posses a synchronized copy of the area's link-state database
- each router constructs its own relative shortest-path tree using the link-state DB, with itself as the root, for all known routes.

Q: What is IS-IS?
A: Intermediate System to Intermediate System
Link state routing protocol
like OSPF, uses Dijkstra Algorithm
doesn't rely on IP to carry routing information (unlike OSPF)

Q: When configuring dynamic routing, what does the "network" statement mean? eg,
#router eigrp 100
#network 192.168.1.0 0.0.0.255
A: Specifying which interfaces should participate in the dynamic routing

Q: You're using a dynamic routing protocol for the network below.  What should you do for the R1 g0/0 port?
A: - advertise the interface with a "network" statement so other routers can learn about it
- use passive-interface to prevent Hello packets from getting sent out!  It's a waste of bandwidth, and potentially a security risk.

Calc Dijkstra for the graph below

Q: Calculate best cost from A using Dijkstra for the graph below:
(source: https://www.youtube.com/watch?v=5GT5hYzjNoo)
A: 1 Start with node A.  Put infinity for unreachable.  Box the lowest.
2 Start new row.  Find the shortest distance without a box from row above, copy it to this new row and put a box around it - this indicates the node you're currently working from.
3 Add boxed cost to the costs to the other nodes, if they're less than the cost on the row above put that new cost in that column, otherwise, copy from prior row.
4 If you can't reach a node from the boxed node, copy the value from the row above it.
5 Go back to 2 until out of nodes.

Q: What is an OSPF LSU?
A: A Link State Update packet.  This packet carries LSAs (routing information)

Q: What is an OSPF LSR?
A: Link State Request - used by a router to request specific LSA (link state advertisement) information from a neighbor

Q: What is an OSPF LSAck?
A: Link State Acknowledgement - used by a router to confirm it received an LSU.

Q: What is the difference between OSPF neighborship and adjacency?
A: Neighbors:
reside on the same network link
exchange Hello messages
Adjacencies:
are neighbors
have exchanged LSU and DBD (Database Descriptor) packets

Q: You have a network running OSPF.  How is the designated router selected?  If an election has already occurred and a new router is added that *could have been* the DR, is that new router set as the DR?
A: Selection:
- highest OSPF priority (eg set by "R1(config-if)#ip ospf priority 255") - note in interface config mode
- tiebreaker: highest router ID (set per router by "R1(config)#router-id id"; if not set, highest loopback; if no loopback highest interface)
No, once the election is done, it's done.

Q: OSPF cost is 10^8 / bandwidth.  For the below network, under default settings, what path would OSPF consider the shortest?
A: Despite higher bandwidth from R1-R2-R3, OSPF would choose R1-R3.  The 1 Gbps link has cost of 10^8 / 10^9, but this is rounded up to 1, as the cost must be an integer, so the total cost over R1-R2-R3 would be 2, and from R1-R3 direct would only be 1.
To fix this, we can set a higher reference bandwidth.  "auto-cost reference-bandwith <value>"
The cost is a 16-bit value.

Q: What is the range of OSPF cost?
A: The cost is a 16-bit value, so it ranges from 1 to 65535.
Note the min cost in 1, so it's possible that links over 100Mbps, such as 1Gbps or 10Gbps, would all be given the same value of 1, and therefore OSPF wouldn't choose the best link.

Q: Suppose we had a company merger and ended up with an OSPF topology like the following.  Is this ok?  What can be done?
A: No, every area has to be adjacent to area 0.
To make this work, we could create a virtual link between router R3 and R7

Q: For the following OSPF network types, a)  say if it uses DR/BDR, b) give the default Hello interval, and c) say if it uses the neighbor command:
Broadcast
Point-to-point
NBMA
Point-to-multipoint
A: If multiple routers, DR/BDR needed.
Point-to-point or -multipoint doesn't need neighbors or DR/BDR.
Non-Broadcast needs neighbor command, b/c it can't find neighbors.

Q: How can you have all of your router's interfaces participate in OSPF in one command?
A: #router ospf 1
#network 0.0.0.0 255.255.255.255 area 0

Q: Do: set up OSPFv3 on a router.  Handle cost calculations, and join all interfaces (make whatever assumptions you need).  Prevent one interface from sending data.
A: _R1(config)#ipv6 unicast-routing
_R1(config)#ipv6 cef
_R1(config)#ipv6 router ospf 1
_%OSPFv3-4-NORTRID: OSPFv3 process 1 could not pick a router-id,please configure manually
_R1(config-rtr)#router-id 1.1.1.1
_R1(config-rtr)#auto-cost reference-bandwidth 10000
_% OSPF: Reference bandwidth is changed.
_        Please ensure reference bandwidth is consistent across all routers.
_R1(config-rtr)#exit
_
_Now set up the interfaces ...
_
_R1(config)#int f0/0
_R1(config-if)#ipv6 ospf 1 area 0
_R1(config-if)#exit
_R1(config)#int f0/1
_R1(config-if)#ipv6 ospf 1 area 0
_R1(config-if)#exit
_
_Task: f0/0 connects out to hosts only, don't send OSPF out that interface.
_R1(config)#ipv6 router ospf 1
_R1(config-rtr)#passive-interface f0/0
_R1(config-rtr)#exit
_R1(config)#exit

Q: When a router is starting up, it needs to find the IOS.  What determines where to look, and what are the possibilities?
A: Bootstrap looks at the Configuration Register, and the value of the rightmost bit determines where to load from.  Eg, 0x2102.
So, "#config-register 0x2100" will boot to ROM Mon.
If the hex digit is "2", it searches for "boot system" in NVRAM.
If it doesn't find "boot system", try load first image in flash.
If it doesn't find in flash, it looks for TFTP.  6 tries.
Then fails to ROM Monitor mode.

Q: What value can you set the config register so the next time it boots it goes into ROM Monitor?
A: 0x2100 - this 0 means "boot to ROM Monitor"
#config-register 0x2100  !boot to ROM Monitor mode
#exit
#reload
If that blue number was 1, it would load from flash; if 2, from NVRAM.

Q: What's the name of the file system on routers and switches?  How do you see them?
A: IFS - integrated file system
eg, has folders like tftp, flash, nvram, etc.
See file systems with "Router#show file systems"

Q: How do you back up a router's startup config to a TFTP server?
A: Router#copy startup-config tftp
Address or name of remote host []? 1.1.1.1
Destination filename [Router-confg]?
Writing startup-config....

Q: Where does a router get its startup config from?
A: After the IOS is expanded into RAM, the IOS software looks for startup-config file stored in NVRAM (file created by "copy run start").  If found, the router loads it into RAM, named as running-config.
If not found, the router will broadcast out any interface that detects carrier detect (CD) for a TFTP host looking for a configuration, and when that fails (typically it will fail), it will start the setup mode configuration process.

Below is a Cisco IOS image.  What are the various parts of the filename?

Q: Do: upgrade a router's IOS image, downloading "somefilename" from tftp server 1.1.1.1, and ensure that image gets used at boot time.
A: First check available memory:
Router#show flash
_System flash directory:
_File  Length   Name/status
_  3   33591768 c1841-advipservicesk9-mz.124-15.T1.bin
_  2   28282    sigdef-category.xml
_  1   227537   sigdef-default.xml
_[33847587 bytes used, 30168797 available, 64016384 total]
_63488K bytes of processor board System flash (Read/Write)
then copy it
_Router#copy tftp: flash:
_Address or name of remote host []? 1.1.1.1
_Source filename []? somefilename
_Destination filename [somefilename]?
_Accessing tftp://1.1.1.1/somefilename....
... downloads
And set it to use that at start
_Router#config t
_Router(config)#boot system flash:somefilename
_Router(config)#exit
Then #copy run start, and #reload

Q: What info do you need to get a license, and where can you get it?
A: Product Authorization Key (PAK)
Cisco License Manager (software, downloadable), or Cisco License Registration Portal
You input your PAK and other info, and are emailed a license file.

Q: What were the old (pre 15.0) feature sets and packages? (familiarity only, don't memorize)
A: Familiarity only:
IP Base: basic features, included in all other feature sets
IP Voice: VoIP and telephony
Advanced Security: eg, IPsec VPNs, IPS, and Cisco IOS Firewall.
SP Services: service provider features, such as MPLS and ATM.
Enterprise Base: multiprotocol support, eg DLSw+, AppleTalk, and IPX protocols.
Advanced IP Services: Advanced Security + Service Provider
Enterprise Services: Enterprise Base + Service Provider
Advanced Enterprise Services: all

Q: What are the four tech package licenses?  How do you get them?
A: IP Base (IPBaseK9): Basic features, all routers come with this.
Security (SECK9): unlocks security features, eg IPsec, Cisco IOS Firewall, and IPS.
Unified Communications (UCK9): unlocks VoIP and IP telephony features, such as the ability for an ISR2 router to act as a video gateway.
Data (DATAK9): unlocks service provider and multiprotocol support, including support for MLPS and IPX.
Unlock these features with licenses.

Q: How do we see what licenses we have installed?
A: #show license

Q: How do we install a permanent license?
A: R1#license install flash:uck9-filename.xml
R1#reload  !activated on reboot
Note not done from config!

Q: How do we install a trial license (that is, activate a Right-to-Use evaluation license already installed in our router)?
A: R1(config)#license boot module c2900 technology-package uck9
ACCEPT? [yes/no]: yes
R1(config)#copy run start
R1#reload   !activated on reboot
you have 60 days

Q: How do you back up licenses?
A: R1#license save flash:kevins_licenses.lic
saves all the licenses

Q: How do you remove a license?
A: First, have to disable it, write, and reboot.
_R1(config)#license boot module c2900 technology-package uck9 disable
_R1(config)#exit
_R1#copy run start
_R1#reload
Then clear it, and remove the "disable" line from the start config!
_R1#license clear uck9
_R1#config t
_R1(config)#no license boot module c2900 technology-package uck9 disable
_R1(config)#end
_R1#copy run start
_R1#reload
After the router reboots, the license is gone.

Q: What tables does CEF (Cisco Express Forwarding) have?
A: FIB - forwarding information base
adjacencies table
#show ip cef
#show adjacency

Q: "show ip eigrp topology" shows successors and feasible successors.  How can you see non-feasible successors?
A: "show ip eigrp topology all-links"

Q: How can you check the route that will be taken for a particular IP?
A: R1#show ip route 192.168.2.1
_Routing entry for 192.168.2.0/24
_Known via "eigrp 1", distance 90, metric 33280, type internal
_  Redistributing via eigrp 1
_  Last update from 10.1.1.14 on FastEthernet0/1, 00:01:49 ago
_  Routing Descriptor Blocks:
_  * 10.1.1.14, from 10.1.1.14, 00:01:49 ago, via FastEthernet0/1
_      Route metric is 33280, traffic share count is 1
_      Total delay is 300 microseconds, minimum bandwidth is 100000 Kbit
_      Reliability 255/255, minimum MTU 1500 bytes
_      Loading 1/255, Hops 2

Q: You're troubleshooting a router's interface, and "show int f0/0" shows a bunch of runts, giants, CRC errors, etc.  What's the first thing you *might* want to do?
A: R1#clear counters
You might be looking at old data.

Q: How many Type 1 LSAs are generated for a given area?
A: One is generated per subnet in an area.

Q: Why is a Type 2 LSA not generated in Area 0 below?
A: Type 2 LSA represents a subnet that has a DR.  Area 1 is ethernet, but R2-R3 is point-to-point, so there is no DR, and hence no Type 2 LSA.

Q: Why is the Type 4 LSA only shown in Area 0?
A: Type 4 tells routers how to get to ASBRs.  Area 1 already knows about it, b/c the ASBR R1 is in Area 1.

Q: You've set R1's OSPF priority to be higher than R2's, but R2 is still the Designated Router.  Why?
A: R2 came up first, and so set itself as the DR.  R1 didn't depose R2 when it came up.

Q: Do: set the Hello timer to 17 seconds for ospf process 1 on a router.
A: #int s0/0/0
#ip ospf hello-interval 17

Q: Do: add plain-text authentication to an OSPF router.
A: RIGHT(config)#int f0/1
RIGHT(config-if)#ip ospf authentication-key cisco
RIGHT(config-if)#exit
RIGHT(config)#router ospf 1
RIGHT(config-router)#area 0 authentication
RIGHT(config-router)#exit
... and do the same for the other router.

Q: Do: add md5 hashed auth for a router's OSPF area 0
A: LEFT(config)#int f0/1
LEFT(config-if)#ip ospf message-digest-key 1 md5 cisco
LEFT(config-if)#exit
LEFT(config)#router ospf 1
LEFT(config-router)#area 0 authentication message-digest
LEFT(config-router)#exit
LEFT(config)#exit

Q: How can you see which interfaces are participating in EIGRP?
A: R1#show ip eigrp interfaces
_IP-EIGRP interfaces for process 1
_
_                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
_Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
_Fa0/0              0        0/0      1236       0/10           0           0
_Fa0/1              1        0/0      1236       0/10           0           0
_Se0/0/0            1        0/0      1236       0/10           0           0

Q: What is the test a route must pass to be considered a Feasible Successor route?
A: Feasibility Condition.  Its Advertised Distance must be lower than the Feasible Distance (FD) of the Successor Route.

Q: What is the EIGRP metric calculation formula, and what is its default form?
A: (this is rounded to the nearest decimal)
Notes:
Bandwidth = (10,000,000 / minimum bandwidth in Kbps)
Delay = sum of egress interface delays in microseconds / 10
default K values K1 = 1, K2 = 0, K3 = 1, K4 = K5 = 0
So default EIGRP Metric = 256 * (Bandwidth + Delay)

Q: You're running EIGRP, and have 2 paths to a network, one with metric 1000, and the other with metric 2000.  Which one will make it into the routing table (provided no other routes with lower admin distance exist)?
A: The metric 1000.
A lower metric is better.  Formula: EIGRP Metric = 256 * ( K1*Bandwidth + K2*Bandwidth)/(256-Load) + K3*Delay) * (K5/(Reliability + K4)))
Notes:
Bandwidth = (10,000,000 / minimum bandwidth in Kbps)
Delay = cumulative egress interface delays (in microseconds) / 10
simplifies with default K values to 256 * (Bandwidth + Delay)
So, a link with higher bandwidth will result in a lower Bandwith component (10^7 / b), and lower delays results in lower Delay component.

Q: EIGRP: Router R1's f0/1 is connected to R2's f0/0.  Both are running EIGRP.  Set up eigrp authentication.
A: Task: set up R1 eigrp auth with key chain DEMO, and first key cisco.
_R1(config)#key chain DEMO
_R1(config-keychain)#key 1
_R1(config-keychain-key)#key-string cisco
_R1(config-keychain-key)#exit
_R1(config-keychain)#exit
_
_# Note:
_# R1(config)#do show ip protocols
_# Routing Protocol is "eigrp  100 "
_
_R1(config)#int f0/1
_R1(config-if)#ip authentication key-chain eigrp 100 DEMO
_R1(config-if)#ip authentication mode eigrp 100 md5
_R1(config-if)#exit
_R1(config)#exit
_
Then set up the same key string on the other router.

Q: These routers are running EIGRP.  R2 can only see its 10.2.2.0/24 network.  It can't see 10.1.1.0/24, even though it has adjacencies with R1 and R3.  What's going on?
Here is the "show ip route" output, note you can only see 10.2.2.0:
A: These are discontiguous subnets - 10.0.0.0 subnets are spread out, and auto-summarization is on.  Turn on "no auto-summary" for EIGRP for all three routers.

Q: Router R1 and R2 are in HSRP.  How will R2 know if R1 goes down?
A: R1 sends a Hello message every 3 seconds (default, can be set to lower)
If R2 doesn't see the Hello message in the Holdtime timer interval, it concludes R1 is down.

Q: In HSRP, what is the time after which the Standby Router becomes the Active Router?
A: Holdtime timer interval.
This must be at least 3 times the Hello interval.

Q: If using HSRP, what are the default Hello and Holdtime values?  How can you make it quicker?
A: default 3 s hello, 10 s holdtime.  Can set these lower.
For sub-1-second times, use version 2, and set timers:
R1(config-if)#standby version 2
R1(config-if)#standby 1 timers msec 100 msec 300

Q: You're debugging HSRP.  What command can you use to help, and what should you do when done?
A: #debug standby terse   !turns it on for events and packets
#u all !turn off all debugging

Q: What is the advertisement time for VRRP?
A: 1 second (configurable)

Q: What is the Virtual MAC address in VRRP?
A: 0000.5e00.01XX

Q: HSRP has a Holdtime interval, what does VRRP have?
A: HSRP default holdtime = 10 s.
VRRP Master Down interval: 3 * master_advertisement_interval + (256 - VRRP_priority)/256

Q: What multicast address does HSRP use (v1, v2)?
A: 224.0.0.2 (v1)
224.0.0.102 (v2)
No DeSiGN

Q: What multicast address does VRRP use?
A: 224.0.0.18
TouGH!!

Q: What is the AVG in GLBP?
A: Active Virtual Gateway.  Responds to ARP requests from hosts and assigns virtual MAC addresses to members of the GLBP group (Active Virtual Forwarders).  Note the ARP destination is the IP of the AVG!  This lets it load balance across multiple routers.

Q: What is an AVF in GLBP?
A: Active Virtual Forwarder.  A member of a GLBP group that discovers an AVG (active virt gateway), based on Hello messages, and learns its virtual MAC address from that AVG.
An AVF can also be an AVG.

Q: You're configuring GLBP.  What are the different values for x below?
#glbp 10 load-balancing x
A: host-dependent
round-robin  (default)
weighted
none
none: AVG responds to ARPs with its own Virtual Forwarder (VF) MAC address
weighted: place a weight on each device, which is advertised to the AVG, and AVG uses that to load balance
host-dependent: MAC of host address determines its VF MAC address.  Some NAT considerations, and don't use it for small number of end hosts. ...
round-robin: MACs used sequentially.

Q: What are some GLBP timers?
A: Hello timer - default 3 sec
Holdtime timer - default 10 s
Redirect timer - how long an AVG will respond to ARP queries with the virtual MAC address of a failed AVF.
Forwarder time-out time - how long a backup AVF will accept frames destined for the virtual MAC address of a failed AVF.

Q: You have a hub-and-spoke setup with Frame Relay (hub R1, spokes R2 and R3).  One spoke's map looks like the below.  Why is that, and what does that mean?
_R2#show frame-relay map
_Serial0/0/0 (up): ip 10.1.1.1 dlci 201, dynamic,
_              broadcast,
_              CISCO, status defined, active
A: Inverse ARP only looks at the other end of the PVC, it doesn't travel "through" the hub.
R2 currently can't reach R3.

Q: You have the following full mesh Frame Relay network:
it's expensive though.  What could you do instead to connect BR1 and BR2?
A: one solution: use frame relay maps

Q: What does "frame-relay map" do?
A: Maps a remote IP to a local DLCI.

Q: What is the problem with setting up a frame-relay map on regular interfaces, and then doing nothing else?
A: Whenever we set up frame-relay map for a DLCI, Inverse ARP is going to be disabled for ip for that DLCI.  If we reboot those routers, they wouldn't Inverse ARP, so they wouldn't be able to reach anyone not explicitly mapped.
Solution: use subinterfaces

Q: What are the two types of subinterfaces in FrameRelay?
A: Point-to-point - uses a single DLCI
Point-to-multipoint - can be associated with multiple DLCIs

Q: When is FrameRelay Multipoint network typically most helpful?
A: When we have a full-mesh or partial-mesh topology, instead of a hub-and-spoke.

Q: A point-to-multipoint interface can have ______ DLCI(s) going out of that interface.
A: more than one DLCI.  eg,

Q: If you're doing point-to-point Frame Relay, what must be a property of the IP ranges for the PVCs?  What about point-to-multipoint?
A: Need to have separate subnets on each point-to-point network!!
Point-to-multipoint can save on address space, because all the PVCs can belong on the same subnet.

Q: By default, how is Frame Relay classified?
A: By default, Frame Relay is classified as a nonbroadcast multi-access (NBMA) network, meaning it doesn’t send any broadcasts such as RIP updates across the network.

Q: Local Management Interface (LMI) is a signaling standard used between your router and the first Frame Relay.  What info does it communicate?
A: - keepalives
- multicasting
- global addressing (never used)
- status of virtual circuits
Your frame-relay lmi-type must match the provider.

Q: What are Solicited Node Multicast Addresses used for?
A: Solicited-Node multicast addresses are used in Neighbor Discovery Protocol for obtaining the layer 2 link-layer addresses of other nodes.

Q: If we have an interface with the IP address fe80::2aa:ff:fe28:9c5a, what will the associated Solicited-Node multicast address be?
A: ff02::1:ff28:9c5a.
ff02::1:ff00:0/104 - solicited node prefix
28:9c5a - taken from the interface ID

Q: How can you configure a router so that it uses only link-local addresses?
A: Corp(config-if)#ipv6 enable
Note this is different from "ipv6 unicast-routing" - this is done on the interface!

Q: What are the ICMP types used during ipv6 autoconfiguration?
A: Two steps to IPv6 autoconfiguration:
Step 1: Host sends RS message FF02::2, ICMP type 133
Step 2: Router sends RA message FF02::1, ICMP type 134

Q: What does default do below?
R1(config-if)#ipv6 address autoconfig default
A: Delivers a default route received from the Corp router, which will be automatically injected it into my routing table and set as the default route.

Q: Your router is connected to another router ... how can you have it autoconfigure its interface, and also pick up a default route? note this is IPv6!
A: R1(config-if)#ipv6 address autoconfig default

What's the structure of an IPv6 global unicast address?

Q: What ipv6 addresses are reserved for references and docs?
A: 3FFF:FFFF::/32
2001:0DB8::/32

Q: What is the structure of an ipv6 header?
A: 40 bytes, only twice as large as ipv4 header
Flow Label marks packets and traffic flows

Q: How is ICMPv6 implemented?
A: It is carried after the basic IPv6 header information as an extension header.  58 = LauGH!!
Type = type of ICMPv6
Code = more details

Q: In IPv4, what protocol is used to allow a host device to tell its local router that it was joining a multicast group, and what replaces it in IPv6?
A: IGMP (Internet Group Management Protocol).  Replaced by ICMPv6, multicast listener discovery.

Q: How does IPv6 allow for routing redundancy?
A: Neighbor discovery.

Q: 3. Which of the following is true when describing a link-local address?
A. Packets addressed to a broadcast address are delivered to a single interface.
B. These are your typical publicly routable addresses, just like a regular publicly routable address in IPv4.
C. These are like private addresses in IPv4 in that they are not meant to be routed over the Internet.
D. These addresses are meant for nonrouting purposes, but they are almost globally unique, so it is unlikely they will have an address overlap.
A: 3 "C. Link-local addresses are meant for throwing together a temporary LAN for meetings or a small LAN that is not going to be routed but needs to share and access files and services locally."

Q: A host sends a router solicitation (RS) on the data link. What destination address is sent with this request?
A: FF02::2

Q: What are the two ways to represent "area 1" for ospf?
A: There are two ways to display the area ID for ospf. The first is in decimal, and the second is in dotted decimal. So area 1 can be both “area 1″ or “area 0.0.0.1″

Q: How many bits are in an IPv6 address field?
A: 16.  There are 8 fields in the address, eg FFFF.xxxx. ..., where FFFF is a field.

Q: Which of the following is true regarding OSPFv3? (Choose three.)
A. Uses a wildcard to define interfaces
B. Uses a network command under global configuration mode
C. Uses a 32-bit router ID
D. Uses link-state advertisements
E. Uses an interface command to enable OSPF on an interface
A: C, D, E. OSPFv3 does not use the network command under global configuration mode, nor does it use wildcard masks as IPv4 does.
However, they can both use the interface command to configure OSPF, use a 32-bit RID, and both use LSAs.

Q: What is STP convergence?
A: When all ports on bridges and switches have transitioned to either forwarding or blocking modes. No data will be forwarded until convergence is complete.

Q: Is 802.1w backwards-compatible with 802.1d?
A: RSTP (802.1w) supersedes 802.1d (STP) while remaining backward compatible.

Q: What are the states in RSTP, and how do they compare with STP?
A: 802.1d => 802.1w (RSTP)
Disabled = Discarding
Blocking = Discarding
Listening = Discarding
Learning = Learning
Forwarding = Forwarding

Q: For STP, if a given switch has two links to another switch (two lines connected via two separate ports), and both have the same bandwidth (cost), which will be chosen as the designated port?
A: The port with the lowest number will be chosen—for example, Fa0/1 would be chosen over Fa0/2.

Q: what is Dense Wavelength Division Multiplexing (DWDM)?
A: different wavelengths (lambda) for different customers.

Q: One way to set the STP bridge priority is, e.g. "spanning-tree vlan 1 priority 4096".  What's the other way?
A: #spanning-tree vlan 1 root primary

Q: How do you enable RSTP on a Cisco switch?
A: S2(config)#spanning-tree mode rapid-pvst
Note this is in global mode, and is not per-vlan.

Q: What problems happen in a network where STP has failed?  How do you fix it?
A: - load on all links increases as more and more frames enter the loop (and affects all others, as frame is flooded out all ports).  May be isolated to a single VLAN.
- more than one loop = multiplicative, circling frames actually get duplicated!
- MAC address table instability, the same source address comes in via multiple ports on the switch.
- due to high load on links and CPU, devices become unresponsive.
At this point your only option is to systematically remove every redundant link between switches until you can find the source of the problem.

Q: What parameters must match for all ports to be grouped via PAgP or LACP?
A: speed, duplex, VLAN info

Q: Which of the following is Cisco proprietary: LACP or PAgP?
A: PAgP

Q: What standard is RSTP PVST+ based on?
A: 802.1w

Q: What command can you use to set a switch so that it will be the root bridge for VLAN 3 over any other switch?
A: spanning-tree vlan 3 priority 0
spanning-tree vlan 3 root primary

Q: You need to find the VLANs for which your switch is the root bridge. What two commands can you use?
A: show spanning-tree
show spanning-tree summary

Q: How many bits is the sys-id-ext field in a BPDU?
A: To allow for the PVST+ to operate, there’s a field inserted into the BPDU to accom- modate the extended system ID so that PVST+ can have a root bridge configured on a per-STP instance. The extended system ID (VLAN ID) is a 12-bit field, and we can even see what this field is carrying via the show spanning-tree command output.

Q: In which circumstance are multiple copies of the same unicast frame likely to be transmitted in a switched LAN?
A: In an improperly implemented redundant topology (with no STP)!

If SB goes through SA to SC, the cost would be 4 + 19, or 23. If SB goes to SA to SD to SC, the cost is 4 + 4 + 4 = 12.

Q: Which of the following are roles in STP? (Choose all that apply.)
A. Blocking
B. Discarding
C. Root
D. Non-designated
E. Forwarding
F. Designated
A: A. Blocking
B. Discarding
C. Root
D. Non-designated
E. Forwarding
F. Designated
20. a, c, d, e, f
The roles a switch port can play in STP are root, non-root, designated, non-designated, forwarding, and blocking. Discarding is used in RSTP, and disabled could be a role, but it’s not listed as a possible answer.

Q: What is the format of a GLBP virtual MAC?
A: 0007.B400.xxyy
GLBP (https://qospf.wordpress.com/2008/06/15/ip-services-hsrp-vrrp-glbp/)
xx is group number
yy is AVF number

Q: What is the format of a VRRP virtual MAC?
A: 0000.5E00.01XX
Breakdown:
- 00005E is IANA's OUI
- 0001 is the address block assigned to the VRRP protocol
- The last byte of the address (XX) is the Virtual Router IDentifier (VRID), which is different for each virtual router in the network.
https://en.wikipedia.org/wiki/Virtual_Router_Redundancy_Protocol

Q: What is the format of an HSRP virtual MAC?
A: v1: 0000.0C07.ACxx, where xx is hex HSRP group
v2: 0000.0C9F.Fxxx, where xxx is hex HSRP group

Q: Match the virtual macs to the FHRP:
0000.5E00.0101
0000.0C07.AC01
0007.B400.0102
0000.0C9F.F001
A: 0000.5E00.0101 - VRRP
0000.0C07.AC01 - HSRP v1
0007.B400.0102 - GLBP
0000.0C9F.F001 - HSRP v2

Q: Do: configure the ipv6 link local address FE80::1
A: R1(config-if)# ipv6 address FE80::1 link-local

Q: which command is used on a pc and which on a router?
tracert, traceroute
A: tracert - use on PC
traceroute - use on router  - traceroute

Q: Which router commands provide information about the lines being used for configuration or device monitoring?
A: > show users

Q: Do: copy the running config to a TFTP server
A: Router# copy running-config tftp
Note: this is in priv exec mode!

Q: How do you ssh to a router from a PC (in packet tracer, at least)?
A: PC>ssh
Usage: SSH -l username target
PC>ssh -l aoeu 10.10.10.1
Open
Password:

Q: Do router config: You want to force someone to wait for three minutes before trying to log in with telnet again, if they've already tried and failed four times within a two-minute period.
A: R1(config)# login block-for 180 attempts 4 within 120
This applies to both Telnet connections and SSH connections.

Q: Do: config router to use ssh v2, allow 2 retries, and time out after 60 seconds.
A: Admin-Sw(config)#ip domain-name cisco.com
Admin-Sw(config)#crypto key generate rsa
The name for the keys will be: Admin-Sw.cisco.com
Choose the size of the key ... How many bits in the modulus [512]: 1024
% Generating 1024 bit RSA keys, keys will be non-exportable...[OK]
Admin-Sw(config)#ip ssh version 2
Admin-Sw(config)#ip ssh time-out 60
Admin-Sw(config)#ip ssh authentication-retries 2
Admin-Sw(config)#line vty 0 15
Admin-Sw(config-line)#transport input ssh
Admin-Sw(config-line)#login local

Q: When troubleshooting ipv6, what is the order you should ping things?
A: default (::1), link local of host's interface, global of host's interface, router link local, router global

Q: Show a router's neighbor resolution table for ipv6.
A: R1#show ipv6 neighbors
IPv6 Address                              Age Link-layer Addr State Interface
2001:DB8:1:1::F                             0 000A.F315.580C  REACH Gig0/0
FE80::20A:F3FF:FE15:580C                    0 000A.F315.580C  REACH Gig0/0

Q: What are the states for ipv6 resolution in "show ipv6 neighbors"?  eg, sample output below:
_R1(config)#do show ipv6 neighbors
_IPv6 Address                              Age Link-layer Addr State Interface
_2001:DB8:1:1::F                             0 000A.F315.580C  REACH Gig0/0
_FE80::20A:F3FF:FE15:580C                    0 000A.F315.580C  REACH Gig0/0
A: INCMP (incomplete): Address resolution in progress (neighbor solicitation sent, no response)
REACH (reachable): path to the neighbor is functioning correctly. REACH is good!
STALE: interface has not communicated within the neighbor reachable time frame.  Changes to REACH the next time the neighbor communicates successfully
DELAY: Can occur after STALE state, if hasn't had communication within a configured timeframe.
PROBE: interface is resending a neighbor solicitation and waiting for a reachability confirmation

Q: What commands can you use on a windows host to check ipv6 default gateway?
A: ipconfig
netsh interface ipv6 show neighbor

Q: What is the temp address below?
_C:\Users\Todd Lammle>ipconfig
_Connection-specific DNS Suffix . : localdomain
_IPv6 Address. . . . . . . . . . . : 2001:db8:3c4d:3:ac3b:2ef:1823:8938
_Temporary IPv6 Address. . . . . . : 2001:db8:3c4d:3:2f33:44dd:211:1c3d
_Link-local IPv6 Address . . . . . : fe80::ac3b:2ef:1823:8938%11
_IPv4 Address. . . . . . . . . . . : 10.1.1.10
_Subnet Mask . . . . . . . . . . . : 255.255.255.0
_Default Gateway . . . . . . . . . : Fe80::21a:6dff:fe37:a44e%11
_10.1.1.1
A: Generated by windows to provide privacy from the EUI-64 format.
fyi only: Can be turned off with:
netsh interface ipv6 set global randomizeidentifiers=disabled
netsh interface ipv6 set privacy state-disabled

Q: Router A and B's f0/1 are connected.  Router B has link-local address FE80::1 on all interfaces.  Make a default static route from A to B using the link-local address of B.
A: R1(config)#ipv6 route ::/0 fastethernet 0/1 FE80::1
Note you can use either Global Unicast IPv6 address or Link-Local IPv6 address as the next hop address. However, if you provide the Link-Local IPv6 address as the next hop address, you need to provide the interface number also.

Q: Quickly outline the Cisco steps in troubleshooting an IPv4/IPv6 network.
A: Check interfaces for errors, check cables
Verify routing path, manipulate route if needed
Verify default gateway
Verify name resolution settings
Verify no ACLs blocking
Verify VLAN database
Verify CAM table
Verify VLAN port assignments
Verify trunking

Q: On windows machines, what commands can you use to verify the ipv4 default gateway?
A: C:\Users\Todd Lammle>ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
   Connection-specific DNS Suffix  . : localdomain
   Link-local IPv6 Address . . . . . : fe80::64e3:76a2:541f:ebcb%11
   IPv4 Address. . . . . . . . . . . : 10.1.1.10
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 10.1.1.1
C:\Users\Todd Lammle>route print
[output cut]
IPv4 Route Table
=======================================================================
Active Routes:
Network Destination      Netmask        Gateway       Interface  Metric
          0.0.0.0        0.0.0.0        10.1.1.10     10.1.1.1   10
[output cut]

Q: What command shows ipv4 and ipv6 access lists, and if it has been applied to an interface?
A: show access-lists
show ipv6 access-lists
show ip int fa0/0
show ipv6 int fa0/0

Q: How can you  check and clear a router's arp cache?
A: R1#show arp
R1#clear arp-cache

Q: How can you check and clear a router's ipv6 neighbors?
A: show ipv6 neighbors
clear ipv6 neighbors

Q: What is the most common cause of errors in ethernet links, and how do you fix them?
A: Most common: mismatched duplex mode between two ends of an Ethernet link - will get many errors.  Telling sign is that the late collision counter will increment.
Different speed: just won't connect.
To fix:
_Switch(config)#int gi0/1
_Switch(config-if)#speed ?
_      10    Force 10 Mbps operation
_      100   Force 100 Mbps operation
_      1000  Force 1000 Mbps operation
_      auto  Enable AUTO speed configuration
_Switch(config-if)#speed 1000
_Switch(config-if)#duplex ?
_      auto  Enable AUTO duplex configuration
_      full  Force full duplex operation
_      half  Force half-duplex operation
_Switch(config-if)#duplex full

Q: What are commands you can use to debug nat?
A: Router#show ip nat translations
Router#debug ip nat

Q: You have a bad NAT entry.  How can you get rid of it?
A: clear ip nat translation
Can use * to clear all

Q: List the advantages and disadvantages of NAT
A: Advantages
Conserves legally registered addresses.
Remedies address overlap events.
Increases flexibility when connecting to the Internet.
Eliminates address renumbering as a network evolves.
Disadvantages
Translation results in switching path delays.
Causes loss of end-to-end IP traceability
Certain applications will not function with NAT enabled

Q: Configure your router to start with flash file c2800nm-advsecurityk9-mz.151-4.M6.bin
A: Router(config)#boot system flash c2800nm-advsecurityk9-mz.151-4.M6.bin

Q: What should you verify before copying a flash image to/from a router?
A: TFTP server software must be running on the laptop or workstation.
Using crossover cable for ethernet connection between the router and the workstation
The workstation must be on the same subnet as the router’s Ethernet interface.
The "copy flash tftp command" must be supplied the IP address of the workstation if you are copying from the router flash.
"show flash" to verify enough room in flash if you’re copying *into* flash

Q: What does ISDN use to transmit data?
A: ISDN Integrated Services Digital Network (ISDN) is a set of digital services that transmit voice and data over existing phone lines.
cost-effective for users who need a higher-speed connection than analog POTS dial-up links can give them, and it’s also a good choice to use as a backup link for other types of links, such as Frame Relay or T1 connections.

Q: What pieces of info are needed to obtain a license for a feature (eg SECK9), and how do you get them?
A: The device UDI and the product authorization key (PAK).
Router#sh license udi
Pak received with purchase

Q: Where can you get a license file?
A: license file from the Cisco License Manager (CLM), which is an automated process, or use the manual process through the Cisco Product License Registration portal.

Q: What is the length of time for a Right-to-Use license?
A: 60 days

Q: What are some Cisco IFS (integrated file system) commands?
A: dir, copy, more, delete, erase or format, cd, pwd, mkdir rmdir

Q: What is the difference between the "show license [all]" and "show license feature" commands?
A: show license: licenses that are active on your system.
show license feature: view the technology package licenses and feature licenses that are supported on your router.

Q: With IOS 15, do you buy and install additional features on routers?
A: With the IOS 15.0 code, the packaging is now called a universal image, meaning all feature sets are available in one file with all features packed neatly inside.

Q: Here is a router mac: 0000.0c07.ac0a. What are the parts?
A: HSRP MAC address
00000c = Cisco
07ac = HSRP v1
0a = standby group

Q: What are the different timers used in HSRP, and some of the defaults?
A: Hello (default 3 seconds): time between packets
Hold (default 10 s, approx 3x Hello): interval the standby router uses to determine if active is offline/out of communication.
Active: monitors the active router's state, is reset when Hello packet received from the active router.
Standby: monitors the standby router's state, is reset when router in the standby group receives a Hello packet from the standby router.

Q: HSRP has a Virtual, Active, and Standby routers.  If other routers are in the group, what do they do?
A: - monitor the Hello messages sent by the active and standby routers to ensure they exist
- forward data that’s specifically addressed to their own IP addresses, but not data addressed to virtual router (unless elected to active or standby)
- send “speak” messages based on the hello timer interval that informs other routers of their position in an election

Q: What is the HSRP default priority?
A: Default priority = 100
This priority comes into play only if both routers were to come up at the same time!

Q: Can you do load balancing with HSRP?
A: HSRP doesn’t really perform true load balancing, but it can be configured to use more than one router at a time for use with different VLANs.  eg, for 2 VLANs, there would be 2 Router-on-a-sticks, and then each would be in a separate HSRP group as the active.

Q: When setting the VRRP master IP, what happens if a real IP is used, and if a virtual IP is used?
A: If a real IP address is used, the router with that address becomes the master.
If a virtual IP address is used, the master is the router with the highest priority.

Q: What are the different members/roles in GLBP?  Describe briefly how they load balance, e.g. with round-robin.
A: GLBP AVG: Members of a GLBP group elect one gateway to be the AVG for that group.  Other group members provide backup for the AVG in the event that the AVG becomes unavailable. The AVG assigns a different virtual MAC address to each member of the GLBP group.
GLBP AVF: Each gateway assumes responsibility for forwarding packets that are sent to the virtual MAC address assigned to that gateway by the AVG. These gateways are known as AVFs for their virtual MAC address.
Load balancing:
1. client sends an ARP message for the gateway IP address, the AVG returns the virtual MAC address of one of the AVFs.
2. When a second client sends an ARP message, the AVG returns the next virtual MAC address from the list.

Q: How can you see which router is active in GLBP?
A: R1#show glbp
R1#show glbp brief

Q: What command adds timestamps to logs, and what command adds sequence numbers?
A: R(config)#service timestamps log datetime msec
R(config)#service sequence-numbers

Q: In PPP, what is NCP, and what are some common examples?
A: There is actually a family of Network Control Protocols (NCPs) for establishing and configuring different network layer protocols. PPP allows the simultaneous use of multiple network layer protocols.
examples: Internet Protocol (IPv4) Control Protocol, IPv6 Control Protocol, AppleTalk Control Protocol, ... etc

Q: If you use "switchport port-security mac-address sticky", where are the sticky MAC addresses stored?
A: In the running config.  They're also stored in the MAC address table.

Q: How can you clear all of the dynamically learned port security MAC addresses on a switch's interface?
A: SW1#clear port-security all interface fa0/1

Q: How many members can be in a GLBP group?
A: Maximum of 4 AVFs. The rest will become Standby Virtual Forwarder (SVF) which will take the place of a AVF in case of failure.

Q: How is the AVG (Active Virtual Gateway) chosen in GLBP?
A: 1. Highest priority
2. If tie, gateway with highest IP address
When the routers are configured to a GLBP group, they first elect one gateway to be the Active Virtual Gateway (AVG) for that group. The election is based on the priority of each gateway (highest priority wins). If all of them have the same priority then the gateway with the highest real IP address becomes the AVG.

Q: What are the differences between SNMPv2 and SNMPv3?
A: SNMPv2:
- uses UDP but can use TCP
- sends data to the NMS station in clear text
SNMPv3:
- uses TCP and authenticates users
- can use ACLs in the SNMP strings to protect the NMS station from unauthorized use.

Q: Which command provides a summary of the NetFlow statistics, including which protocols are in use?
A: R2#show ip cache flow
_IP packet size distribution (0 total packets):
_   1-32   64   96  128  160  192  224  256  288  320  352  384  416  448  480
_   .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
_
_    512  544  576 1024 1536 2048 2560 3072 3584 4096 4608
_   .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
_
_IP Flow Switching Cache, 0 bytes
_  0 active, 0 inactive, 0 added
_  2 ager polls, 0 flow alloc failures
_  Active flows timeout in 30 minutes
_  Inactive flows timeout in 15 seconds
_  last clearing of statistics never
_Protocol         Total    Flows   Packets Bytes  Packets Active(Sec) Idle(Sec)
_--------         Flows     /Sec     /Flow  /Pkt     /Sec     /Flow     /Flow
_Total:               0      0.0         0     0      0.0       0.0       0.0
_
_SrcIf         SrcIPaddress    DstIf         DstIPaddress    Pr SrcP DstP  Pkts

Q: What are the two pieces needed for NetFlow to gather data? (Choose two.)
A. An SNMP NMS station
B. Collector
C. Syslog configured
D. NetFlow-configured router
A: B, D. You need to have a Cisco router to run the proprietary NetFlow application, plus you need a server to send the information to, and this is called a collector.

Q: What are the different logging destinations for Cisco devices, and how do you turn them on/off?
A: Logging buffer (on by default)
Console line (on by default)
Terminal lines (using the terminal monitor command)
Syslog server
Router(config)#no logging console
Router(config)#no logging buffered
To turn these on:
vty: #terminal monitor
syslog: #logging 1.1.1.1

Q: How do you see a router's current logging levels, destination, etc?
A: R1#show logging

Q: Which command will verify the DTP status on a switch interface?
A: #show dtp interface f0/1

Q: The following output was generated by which command?
^IPv6 Address  Age Link-layer Addr State Interface
^FE80::21A:6DFF:FE64:9B3         0 001a.6c46.9b09  DELAY Fa0/1
^2001:DB8:3C4D:2:21A:6DFF:FE64:9B3       0 001a.6c46.9b09  REACH Fa0/1
A: #show ipv6 neighbors

Q: Which commands will show you if you have a native VLAN mismatch?
A. show interface native vlan
B. show interface trunk
C. show interface f0/0 switchport
D. show switchport interface
A: A. show interface native vlan
B. show interface trunk
C. show interface f0/0 switchport
D. show switchport interface
These show statistics of ports, which includes native VLAN information.

Q: You connect two new Cisco 3560 switches together and expect them to use DTP and create a trunk. However, when you check statistics, you find that they are access ports and didn’t negotiate. Why didn’t DTP work on these Cisco switches?
A. The ports on each side of the link are set to auto trunking.
B. The ports on each side of the link are set to on.
C. The ports on each side of the link are set to dynamic.
D. The ports on each side of the link are set to desirable.
A: A. Most Cisco switches ship with a default port mode of auto, meaning that they will automatically trunk if they connect to a port that is on ("switchport mode trunk") or desirable ("switchport mode dynamic desirable").
Remember that not all switches are shipped as mode auto, but many are, and you need to set one side to either on or desirable in order to trunk between switches.

Q: If you have a switch port with setting "switchport mode dynamic auto" connected to another switch, in which of the following will the line be trunked?
opposite switch's port is:
switchport mode dynamic auto
switchport mode dynamic desirable
switchport mode trunk
switchport nonegotiate
switchport mode access
A: switchport mode dynamic auto - NO
switchport mode dynamic desirable - YES
switchport mode trunk - YES
switchport nonegotiate - NO
switchport mode access - NO
"dynamic auto" makes the interface able to convert the link to a trunk link, but it only becomes a trunk interface if the neighboring interface is set to trunk or desirable mode.

Q: Corp router is running OSPF.  The only route in the routing table is via G0/1, due to its higher bandwidth.  How can you get OSPF to *also* use s0/0/0?
A: Fix the cost.
Corp#config t
Corp(config)#int g0/1
Corp(config-if)#ip ospf cost 10
Corp(config-if)#int s0/0/0
Corp(config-if)#ip ospf cost 10

Q: Is the below area ID valid?
Router(config-if)#ipv6 ospf 10 area 0.0.0.0
A: Yes, this is the same as area 0.  You can write it as decimal or as IP, which is converted to decimal.
The Area ID may be expressed either as a decimal number or in dotted decimal.  For example, area 0 and area 0.0.0.0 are equivalent, as are area 16 and area 0.0.0.16, and area 271 and area 0.0.1.15.

Q: What LSA types are sent by ABR toward the area external to the one in which they were generated?
A: Type 3, possibly 4 or 5

Q: True/False: OSPFv3 is configured per area, per interface.
A: True.

Q: What command generated the following?
^GigabitEthernet0/0 is up, line protocol is up
^  Internet address is 10.10.10.1/24, Area 0
^  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
^  Transmit Delay is 1 sec, State DR, Priority 1
^  Designated Router (ID) 1.1.1.1, Interface address 10.10.10.1
^  No backup designated router on this network
^  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
^    Hello due in 00:00:05
^  Index 1/1, flood queue length 0
^  Next 0x0(0)/0x0(0)
^  Last flood scan length is 1, maximum is 1
^  Last flood scan time is 0 msec, maximum is 0 msec
^  Neighbor Count is 0, Adjacent neighbor count is 0
^  Suppress hello for 0 neighbor(s)
A: Corp#sh ip ospf interface gi0/0

Q: Which of the following are scalability issues with single-area OSPF networks? (Choose all that apply.)
A. Size of the routing table
B. Size of the OSPF database
C. Maximum hop-count limitation
D. Recalculation of the OSPF database
A: A. Size of the routing table
B. Size of the OSPF database
C. no
D. Recalculation of the OSPF database
A,B,D. As the size of a single-area OSPF network grows, so does the size of the routing table and OSPF database that have to be maintained. Also, if there is a change in network topology, the OSPF algorithm has to be rerun for the entire network.

Q: Which OSPF state do two routers forming an adjacency appear as in the show ip ospf neighbor output after adding neighbors into the table and exchanging hello information?
A: 2WAY.  The process starts by sending out Hello packets.  Every listening router will then add the originating router to the neighbor database. The responding routers will reply with all of their Hello information so that the originating router can add them to its own neighbor table. At this point, we will have reached the 2WAY state—only certain routers will advance beyond this to establish adjacencies.

Q: Which is/are true regarding OSPFv3? (Choose all that apply.)
A. You must add network statements under the OSPF process.
B. There are no network statements in OSPFv3 configurations.
C. OSPFv3 uses a 128-bit RID.
D. If you have IPv4 configured on the router, it is not mandatory that you configure the RID.
E. If you don’t have IPv4 configured on the router, it is mandatory that you configure the RID.
F. OSPFv3 doesn’t use LSAs like OSPFv2 does.
A: B. There are no network statements in OSPFv3 configurations.
D. If you have IPv4 configured on the router, it is not mandatory that you configure the RID.
E. If you don’t have IPv4 configured on the router, it is mandatory that you configure the RID.
Configuring OSPFv3 is pretty simple, as long as you know what interfaces you are using on your router. There are no network statements, OSPFv3 is configured on a per-interface basis. OSPFv2 and OSPFv3 both use a 32-bit RID, have an IPv4 address configured on at least one interface, you do not need to manually set a RID when con- figuring EIGRPv3.

Q: Using the following illustration, which of the following are true? (Choose all that apply.)
A. R1 is an internal router.
B. R3 would see the networks connected to the R1 router as an inter-area route.
C. R2 is an ASBR.
D. R3 and R4 would receive information from R2 about the backbone area, and the same LSA information would be in both LSDBs.
E. R4 is an ABR.
A: B, D. Since R3 is connected to area 1 and R1 is connected to area 2 and area 0, the routes advertised from R3 would show as OI, or inter-area routes.

Q: Suppose you do the following:
Corp(route)#router ospf 1
Corp(config-router)#auto-cost reference-bandwidth 1000000000
What must you be sure to do?
A: Make sure all the routers within the OSPF AS have the same reference bandwidth.

Q: What is the default cost of a serial interface with OSPF?
A: Default reference bandwidth for OSPF is 100000000 (10^8).  Anything Fast Ethernet or above would have a default cost of 1, and serial interfaces have a default cost of 64.
serial = T1 = 1.544 Mbps = 1.544 * 10^6
10^8 / (1.544 * 10^6) = (1/1.544) * 100 =~ 100 * 2/3   :-)

Q: What are the main differences between DSL and cable?
A: DSL (Digital Subscriber Line)
- runs on telephone lines, using unused frequency ranges
- requires active phone line (POTS, or run a new line)
- dedicated line
- affected by distance - if you're phyically close, can be very fast; if far, may not be eligible
Cable
- runs on coaxial cable lines which run to your home (hybrid fiber-coaxial (HFC))
- uses unused channels (predefined frequency ranges) to pass your data instead of television programming
- shared conection
- heavily shielded coax cables, not affected by distance

Q: WAN term: What's another term for Central Office (CO)?
A: A point of presence (POP).

Q: What's are T1s (1.544 Mbps) and T3s (44.736 Mbps) also referred to as?
A: DS1, DS3

Q: What's a Digital Signal 0?
A: Digital Signal 0 (DS0), the basic digital signaling rate of 64 Kbps, equivalent to one channel (smallest-capacity digital circuit).  Generic term used by several multiplexed digital carrier systems.
Europe uses the E0, Japan J0
1 DS0 = 1 voice/data line.

Q: What's the bandwidth of an OC-3?
A: 155.52 Mbps.
OC-12 and OC-48 are multiples of that.

Q: What are some examples of dedicated, circuit-switched, and packet-switched WANs?
A: dedicated (leased-line): HDLC, PPP
circuit-switched: modem, ISDN (low-bandwidth data transfers)
packet-switched: MPLS, Frame Relay (bursty)

Q: Frame Relay, ISDN, HDLC, PPP, PPPoE, cable, DSL, MPLS, ATM, 3G/4G, VSAT, and Metro Ethernet are all examples of what?
A: WAN protocols

Q: What encapsulations are used over ATM and DSL?
A: PPPoE: PPP over Ethernet, encapsulate PPP frames in Ethernet frames
RFC1483: describes two different methods for carrying connectionless network traffic over an ATM network: routed protocols and bridged protocols.
PPPoA: PPP over ATM is used to encapsulate PPP frames in ATM AAL5 (ATM Adaptation Layer 5).

Q: What type of Cisco-proprietary physical connector was used for serial connections on older routers?
A: Older Cisco routers have used a proprietary 60-pin serial connector that you have to get from Cisco or a provider of Cisco equipment.

Q: When you're connecting a serial line from your router to a service-provider demarc, what type of cable ending will you need?
A: Depends on the service provider:
EIA/TIA-232 - Allowed speed up to 64 Kbps on 24-pin connector
EIA/TIA-449
V.35 — Standard used to connect to a CSU/DSU, with speeds up to 2.048 Mbps using a 34-pin rectangular connector
EIA-530

Q: What layers is PPP specified at?
A: Physical and Data Link layers only. NCP is used to allow communication of multiple Network layer protocols by identifying and encapsulating the protocols across a PPP data link.

Q: What are the two frame relay encapsulation types?
RouterA(config)#int s0
RouterA(config-if)#encapsulation frame-relay ?
A: Cisco or IETF (Internet Engineering Task Force, RFC1490 encapsulation)
For Cisco routers, default is Cisco.  Use ietf is connecting cisco and non-cisco.
Note this is different from the LMI types (Cisco, ANSI, Q.933A)

Q: How do you see the IP-to-DLCI mappings on a frame relay router?
A: show frame-relay map

Q: If your router doesn't support IARP (inverse ARP), how do you associate DLCIs and IPs?
A: frame-relay map ip <remote-ip> <local-dlci>

Q: How do you tell a subinterface its DLCI?
A: RouterA(config-if)#frame-relay interface-dlci 16

Q: If users are complaining about their frame relay speed, what is the first command you should use?
A: RouterA#sh frame-relay pvc
check errors, fecn/becn

Q: You have a Cisco router and a non-Cisco router at two ends of a Frame Relay network.  You've configured one router as below, and the routers aren't communicating.  What's one obvious problem?
_RouterA#config t
_RouterA(config)#int s0/0
_RouterA(config-if)#encapsulation frame-relay
_RouterA(config-if)#ip address 172.16.20.1 255.255.255.0
_RouterA(config-if)#frame-relay lmi-type ansi
_RouterA(config-if)#frame-relay interface-dlci 101
A: "#encapsulation frame-relay" is defaulting to Cisco, and should be ietf.

Q: How do you see the LMI traffic statistics exchanged between the local router and the Frame Relay switch?
A: #show frame-relay lmi

Q: You have the below config on a frame-relay router, but the other router isn't getting the RIP updates.  Why?
_RouterA#show running-config
_interface s0/0
_  ip address 172.16.100.2 255.255.0.0
_  encapsulation frame-relay
_  frame-relay map ip 172.16.100.1 100
_router rip
_network 172.16.0.0
A: Frame Relay is nonbroadcast multi-access (NBMA) network by default, meaning that it doesn’t allow any broadcasts across the PVC.  Have to specify broadcast as part of the map.
  frame-relay map ip 172.16.100.1 100 broadcast

Q: What are the PPP Data Link layer protocols?
A: Network Control Protocol (NCP), which defines the Network layer protocols
Link Control Protocol (LCP), a method of establishing, configuring, maintaining, and terminating the point-to-point connection
High-Level Data-Link Control (HDLC), the MAC layer protocol that encapsulates t

Q: Can you use Ethernet as a WAN?
A: Yes, with Ethernet over MPLS (EoMPLS)

Q: You need to configure a router for a Frame Relay connection to a non-Cisco router.  How do you do that?
A: Router(config-if)#encapsulation frame-relay ietf

Q: Clocking on a serial interface is always provided by what?
A: Clocking on a serial interface is always provided by the CSU/DSU (DCE device). However, if you do not have a CSU/DSU in your nonproduction test environment, then you need to supply clocking with the clock rate command on the serial interface of the router with the DCE cable attached.

Q: How can you see the authentication process that PPP uses across point-to-point connections?
A: #debug ppp authentication

Q: To provide security in your VPN tunnel, what protocol suite would you use?
A: IPSec

Q: Write the commands to configure a remote office using a point-to-point frame-relay subinterface. Use DLCI 16 and IP address 172.16.60.1/24.
A: int s0/0
no ip address
encap frame-relay
frame-relay lmi-type ansi
no shut
int s0/0.16 point-to-point
ip address 172.16.60.1 255.255.255.0
frame-relay interface-dlci 16

Q: What is PPPoE, and what does it allow?
A: - a network protocol for encapsulating PPP frames inside Ethernet frames
- uses common PPP features like authentication, encryption, and compression
- allows authenticated assignment of IP addresses
- the PPPoE client and server are interconnected by Layer 2 bridging protocols running over a DSL or other broadband connection.
- the opposite side of the link’s IP address is given to it and it’s available only for the specific period that the PPPoE connection is open

Q: What are the two main phases of PPPoE?
A: Active Discovery Phase: the PPPoE client locates a PPPoE server, called an access concentrator, and discovers its MAC address. Session ID is assigned and the PPPoE layer is established.   (Discovery is a client-server relationship)
PPP Session Phase: PPP options are negotiated and authentication is performed.
Once completed, PPPoE functions as a Layer 2 encapsulation method, and data is transferred over the PPP link within PPPoE headers.

Q: Why is the MTU for a PPPoE DSL configuration reduced from 1500 bytes to 1492?
A: to accommodate the PPPoE headers  (8 bytes)

Q: What is a virtual-access interface, and a virtual-template interface?
A: virtual-access interface
- a virtual interface that is created, configured dynamically, used, and then freed when no longer needed
- not configured manually - it uses a virtual template interface and/or RADIUS and TACAC+ authentication servers, which results in a VAI that is uniquely config'd for a specific user
virtual-template interface
- a logical entity that can be used to apply predefined interface configurations for virtual-access interfaces as needed
- configured independently of any physical interface

Q: What does "R1#(config)vpdn enable" do?
A: - enables virtual private dialup networking (VPDN) on the router, and informs the router to look for tunnel definitions in a local database and on a remote authorization server (home gateway), if one is present

Q: What is the following packet?
IP: s=172.16.22.1 (FastEthernet0/0), d=224.0.0.5, len 72, rcvd 0, proto=89
A: An OSPF "Hello" packet destined to all OSPF routers on the FastEthernet0/0 network segment.

Q: Is ISL (inter-switch link) an open standard?
A: No, ISL is Cisco proprietary.  Dot1q (802.1q VLAN Tagging) is IEEE standard.

Q: Which OSI layers perform error detection and recovery functions?
A: The Data Link layer performs error detection on incoming packets. Networks often use cyclic redundancy check (CRC) algorithms to find corrupted data at this level.
The Transport layer handles error recovery. It ultimately ensures data are received in order and free of corruption.

Q: What is the default CDP timer intervals?
A: 60 seconds for advertising. to reset, "no cdp timer"
180 s for hold.

Q: What are the Cisco password types and their crackability?
A: Cisco Type 0 Password: These passwords are stored in IOS configuration as plaintext. Least secure.
Cisco Type 5 Password: These passwords are stored as MD5 UNIX hashes which are salted. Most secure.
Cisco Type 7 Password: These passwords are stored in a Cisco defined encryption algorithm. Not secure except for protecting against shoulder surfing attacks.

Q: Create and apply IPv6 access lists.
One list should block http and https traffic from any host to a given ipv6 address, and allow all other.  Apply this to a router interface.
The other list should block all icmp, but allow all other traffic.
Make any assumptions necessary.
Note: not req'd for CCNA, for familiarity only.
A: Limited to named ACLs for ipv6
R1(config)#ipv6 access-list BLOCK_HTTP
R1(config-ipv6-acl)#deny tcp any host 2001:DB8:1:30::30 eq www
R1(config-ipv6-acl)#deny tcp any host 2001:DB8:1:30::30 eq 443
R1(config-ipv6-acl)#permit ipv6 any any
R1(config-ipv6-acl)#exit
R1(config)#int g0/1
R1(config-if)#ipv6 traffic-filter BLOCK_HTTP in
R3(config)#ipv6 access-list BLOCK_ICMP
R3(config-ipv6-acl)#deny icmp any any
R3(config-ipv6-acl)#permit ipv6 any any
R3(config-ipv6-acl)#exit
R3(config)#int g0/0
R3(config-if)#ipv6 traffic-filter BLOCK_ICMP out

Q: Show how to autoconfig a router's interface address using ipv6 autoconfigure, and with ipv4 dhcp.
A: R1(config)#int g0/0
R1(config-if)#ipv6 address autoconfig [default]  !note that default pulls over the active routes
R2(config)#int g0/0
R2(config-if)#ip address dhcp

Q: Set up DHCP for ipv4 for a router on the 192.168.10.0/24 network.  Don't assign the first 10 addresses.  The router's interface is at the first IP in that network.  The name server is at 192.168.20.254.
A: R2(config)#ip dhcp excluded-address 192.168.10.1 192.168.10.10
R2(config)#ip dhcp pool R1-LAN
R2(dhcp-config)#network 192.168.10.0 255.255.255.0
R2(dhcp-config)#default-router 192.168.10.1
R2(dhcp-config)#dns-server 192.168.20.254
N
DR
DS
Note: even if there wasn't a requirement to exclude 10 addresses, you still have to exclude the router's address!

Q: How do you set the lease time for a DHCP pool in a router?
A: Router(dhcp-config)# lease {days [hours][minutes] | infinite}

Q: Configure R2 with a NAT pool that uses all four addresses in the 209.165.76.196/30 address space, and that is used for all addresses belonging to 172.16.0.0/16.
A: R2(config)#access-list 1 permit 172.16.0.0 0.0.255.255
R2(config)#int s0/0/1
R2(config-if)#ip nat inside
R2(config-if)#int s0/0/0
R2(config-if)#ip nat outside
R2(config-if)#exit
R2(config)#ip nat pool X 209.165.76.196 209.165.76.200 netmask 255.255.255.252
THIS IS WRONG!
%Pool X mask 255.255.255.252 too small; should be at least 255.255.255.248
%Start and end addresses on different subnets
R2(config)#ip nat pool X 209.165.76.196 209.165.76.199 netmask 255.255.255.252
R2(config)#ip nat inside source list 1 pool X overload

Q: Port forwarding: you want ppl connecting to TCP port 80 of R2's outside interface to be forwarded to R1's port 80.  Configure NAT!
A: R2(config)#interface FastEthernet 0/0
R2(config-if)#ip nat inside
R2(config)#interface FastEthernet 0/1
R2(config-if)#ip nat outside
R2(config)#ip nat inside source static tcp 192.168.12.1 80 192.168.23.2 80
[Note the page I saw had "extendable" at the end]

Q: In OSPF, and maybe other protocols, what's a catch to bear in mind with "default-information originate"?
A: It *appears* that the default route has to already exist!
I had a lab where both a default route and "default-information originate" were present, but the route wasn't propagated.  I removed the "default-information originate" and re-added it, and it propagated.
The workaround for this is to use "default-information originate always"  !

Q: How can you see a nice listing, like "show ip int brief", which *also* shows the network masks?
A: #show protocols
_R1#show protocols
_Global values:
_  Internet Protocol routing is enabled
_GigabitEthernet0/0 is administratively down, line protocol is down
_GigabitEthernet0/1 is administratively down, line protocol is down
_Serial0/0/0 is up, line protocol is up
_  Internet address is 10.1.1.2/30
_Serial0/0/1 is up, line protocol is up
_  Internet address is 209.165.200.226/30
_Vlan1 is administratively down, line protocol is down

Q: You're setting up a router for Router-on-a-Stick VLAN routing, and want the networks to be propagated with OSPF.
Info:
_VLAN 1
_network 192.168.1.192 255.255.255.224
_ipv6 address 2001:DB8:A:1::1/64 (FE80::2)
_
_VLAN 99 (native)
_network 192.168.1.224 255.255.255.224
_ipv6 address 2001:DB8:A:99::1/64 (FE80::2)
Use the first IP in the range as the interface IP, and use G0/0.
A: _R2(config)#int G0/0.1
_R2(config-subif)#encapsulation dot1q 1
_R2(config-subif)#ip address 192.168.1.193 255.255.255.224
_R2(config-subif)#ipv6 address 2001:DB8:A:1::1/64
_R2(config-subif)#ipv6 address FE80::2 link-local
_
_R2(config)#int G0/0.99
_R2(config-subif)#encapsulation dot1q 99 native
_R2(config-subif)#ip address 192.168.1.225 255.255.255.224
_R2(config-subif)#ipv6 address 2001:DB8:A:99::1/64
_R2(config-subif)#ipv6 address FE80::2 link-local
_
_R2(config)#int g0/0
_R2(config-if)#no ip address
_R2(config-if)#no shut
_
_...
_
_R2(config)#router ospf 1
_R2(config-router)#router-id 2.2.2.2
_R2(config-router)#network 192.168.1.192 0.0.0.31 area 0
_R2(config-router)#network 192.168.1.224 0.0.0.31 area 0
_
_R2(config)#ipv6 router ospf 1
_R2(config-if)#int G0/0.1
_R2(config-subif)#ipv6 ospf 1 area 0
_R2(config-subif)#int g0/0.99
_R2(config-subif)#ipv6 ospf 1 area 0

Q: You're running EIGRP on your routers (AS=100).  Create a static default route exiting s0/0/1, and ensure it propagates to all other routers.
A: R1(config)#ip route 10.1.200.0 255.255.255.0 10.0.0.4
R1(config)#router eigrp 100
R1(config-router)#redistribute static

Q: Router R2 uses Cisco encapsulation.  Its local DLCI 204 should go to next hop address 10.0.0.4 on router R4.  R4 uses IETF encapsulation.  Both routers use EIGRP, so routes should propagate.  Set that map up, and set up frame-relay on router R4.
A: R2(config-if)#frame-relay map ip 10.0.0.4 204 ietf broadcast
R4(config)#int s0/0/0
R4(config-if)#encap frame-relay ietf
R4(config-if)#frame-relay lmi-type ansi

Q: What is SLAAC?
A: Stateless Address Auto-Configuration: the most common method for IPv6 client address assignment.

Q: Do: Set up your router as an ipv6 DHCP server so that hosts connected to g0/0 get an ipv6 address.  Make whatever assumptions are necessary.
A: R1(config)#ipv6 dhcp pool R1_LAN
R1(config-dhcpv6)#prefix-delegation pool ADDRESS_POOL
R1(config-dhcpv6)#dns-server 2001:DB8:CC1E:A::2
R1(config-dhcpv6)#exit
R1(config)#ipv6 local pool ADDRESS_POOL 2001:DB8:ACAD:A::1/64 64
R1(config)#int g0/0
R1(config-if)#ipv6 dhcp server R1_LAN
R1(config-if)#ipv6 nd managed-config-flag
Notes:
"prefix-delegation pool ADDRESS_POOL" - specifies pool
"ipv6 local pool ADDRESS_POOL xxx::/64 64" - pool has prefix length 64, will delegate length 64 as well!
"ipv6 nd managed-config-flag" - tells hosts to use stateful autoconfiguration to obtain addresses
ipv6 nd = IPv6 Neighbor Discovery

Q: In IPv6, what is a Fully Specified Static Route?
A: both the output interface and the next hop are specified.
This form of static route is used when the output interface is a multi-access one and it is necessary to explicitly identify the next hop. The next hop must be directly attached to the specified output interface. The following example shows a definition of a fully specified static route:
ipv6 route 2001:DB8:/32 ethernet1/0 2001:DB8:3000:1
A fully specified route is valid (that is, a candidate for insertion into the IPv6 routing table) when the specified IPv6 interface is IPv6-enabled and up

Q: Do: your router is running EIGRPv3 (AS = 100).  Int g0/0 and g0/1 are for networks 2001:db8:cafe:2::/64 and 2001:db8:cafe:3::/64 respectively.  Advertise a summary route for these out of s0/0/1.
A: R3(config)#int s0/0/1
R3(config-if)#ipv6 summary-address eigrp 100 2001:db8:cafe:2::/63

Q: Do: set up a default ipv6 route leaving interface g0/0.  g0/0 has 2001:DB8:ACAD:F::2/64, it is connected to another router with unicast address 2001:DB8:ACAD:F::1.
A: R2(config)#ipv6 route ::/0 2001:DB8:ACAD:F::1

Q: Do: set up a default ipv6 route leaving interface g0/0 which has link local address fe80::2, going to another router with link local fe80::1.
A: R2(config)#ipv6 route ::/0 g0/0 fe80::1

Q: What are characteristics of a switch?
A: high port density
large frame buffers
support for a mixture of port speeds
fast internal switching
low cost per port

Q: You have a Layer 3 switch.  You want it to act as default gateway for some hosts.  You also want it to connect to a router.  Set that up, make any assumptions necessary.
A: !Set up line to other router:
Switch(config)#int g0/1
Switch(config-if)#no switchport
Switch(config-if)#ip address 192.168.0.2 255.255.255.0
Switch(config-if)#no shut
!Set up as default gateway for vlan
Switch(config-if)#int vlan 1
Switch(config-if)#ip address 172.16.31.1 255.255.255.0
Switch(config-if)#no shut

Q: In classic spanning tree, which switches produce BPDU packets?
A: In classic spanning tree the root switch is the only switch allowed to produces a BPDU (Bridge Protocol Data Unit) packet. By default these packets are sent out every port of the root switch every two seconds. Other switches forward BPDU packets out of all non-blocked ports.

Q: What are the states that an 802.1d spanning tree port transitions through, and what is happening during that state?
A: Blocking (receives BPDU’s - does not process them, asks “am I the root?”)
Listening (sends, receives and PROCESSES BPDUs only – no Ethernet traffic)
Learning (creates a MAC database – does not forward)
Forwarding – acts like a full switch

Q: Configure PPPoE on your router (assume you're setting up the client).
A: ! First, make a dialer, so you can dial in to the central office
R2(config)# int dialer 1
R2(config-if)# encap ppp
R2(config-if)# ip address negotiated  ! get it from the provider
! Set up CHAP username and password
R2(config-if)# ppp chap hostname ISProuter
R2(config-if)# ppp chap password ISPpassword
! PPPoE header takes 8 bytes, so have to change MTU
R2(config-if)# ip mtu 1492
! Have to tell the dialer what pool it's part of
R2(config-if)# dialer pool 1
R2(config-if)# exit
! Now have to actually apply it to an interface
R2(config)# int f0/0
R2(config-if)# pppoe enable
R2(config-if)# pppoe-client dial-pool-number 1