Title: Cisco / CCNA-200-125 / ICND1-100-105
Tags: Network-Fundamentals Switching-Technologies Infrastructure-Management Routing-Technologies Key-Concepts Additional-Depth Spanning-Tree

Q: List the layer numbers and names of the OSI model
A: 1. Physical
2. Data Link
3. Network
4. Transport
5. Session
6. Presentation
7. Application

Q: List the layer names of the original TCP/IP model, and which OSI layers they correspond with
A: Link: OSI 1-2
Internet: OSI 3
Transport: OSI 4
Application: OSI 5-7

Q: List the layer names of the revised TCP/IP model, and which OSI layers they correspond with
A: Physical: OSI 1
Data Link: OSI 2
Network: OSI 3
Transport: OSI 4
Application: OSI 5-7

Term: OSI Physical Layer
Definition: protocols which define the physical characteristics of the transmission
medium, including connectors, pins, use of pins, electrical currents, encoding, light
modulation, and so on

Term: OSI Data Link Layer
Definition: protocols which deliver data over a particular single type of physical network

Term: OSI Network Layer
Definition: protocols which provide for logical addressing, forwarding, and learning routes

Term: OSI Transport Layer
Definition: protocols which provide for data delivery between the two endpoint hosts

Term: OSI Presentation Layer
Definition: protocols which negotiate data formats

Term: OSI Application Layer
Definition: protocols which form an interface from the application to the network which supply actions meaningful to the application

Acronym: PDU
Term: Protocol Data Unit
Definition: a group of information, including headers and trailers, belonging to a specific protocol

Term: Frame
Definition: the Ethernet data unit

Term: Packet
Definition: the IP data unit
Other fields (not shown on cards):
Additional Info: Although commonly used for many different data bundles, the term is specific to the IP protocol

Term: Segment
Definition: the TCP data unit
Other fields (not shown on cards):
Additional Info: Although commonly used for all L4 PDUs, the term is specific to the TCP protocol

Q: What are some benefits of using a network model?
A: - Less complex: Compared to not using a layered model, network models break the concepts into smaller parts.
- Standard interfaces: The standard interface definitions between each layer allow multiple vendors to create products that fill a particular role, with all the benefits of open competition.
- Easier to learn: Humans can more easily discuss and learn about the many details of a protocol specification.
- Easier to develop: Reduced complexity allows easier program changes and faster product development.
- Multivendor interoperability: Creating products to meet the same networking standards means that computers and networking gear from multiple vendors can work in the same network.
- Modular engineering: One vendor can write software that implements higher layers—for example, a web browser—and another vendor can write software that implements the lower layers—for example, Microsoft’s built-in TCP/IP software in its operating systems.

Term: Same-Layer Interaction
Definition: one protocol communicating with a related protocol on another computer

Term: Adjacent-Layer Interaction
Definition: when, on a single computer, one layer provides a service to a higher layer, or requests a service from a lower layer

Term: Encapsulation
Definition: the process of putting headers (and sometimes trailers) around some data

Term: Deencapsulation
Definition: the process of removing headers (and sometimes trailers) around some data

Term: Networking Model
Definition: a comprehensive set of documents or standards which define everything necessary for a computer network to work

Term: Routing
Definition: inspecting an IP header and comparing the address to a routing table to determine where to forward the packet

Term: Switching
Definition: inspecting the Ethernet header and comparing the address to a table to determine which ports to send the frame out on
Other fields (not shown on cards):
Additional Info: The table is commonly referred to as a MAC or CAM table

Acronym: LAN
Term: Local Area Network
Definition: a group of networking and attached devices in a local geographic area
Other fields (not shown on cards):
Additional Info: The geographic size will differ greatly between organizations, but the technologies used or the operaters of a LAN differ from that of a WAN

Acronym: WAN
Term: Wide-Area Network
Definition: a network spread over a wide geographic area
Other fields (not shown on cards):
Additional Info: The geographic size will differ greatly between organizations, WANs are generally used to connect LANs together

Q: SOHO
A: Small Office / Home Office

Q: IT
A: Information Technology

Acronym: TCP
Term: Transport Control Protocol
Definition: an L4 protocol on top of IP that provides service identification through Ports and transmission control through windowing and acknowledgments

Acronym: UDP
Term: User Datagram Protocol
Definition: an L4 protocol on top of IP that provides service identification through Ports but no message acknowledgment or flow control

Q: URL
A: Uniform Resource Locator

Q: URI
A: Uniform Resource Identifier

Q: HTTP
A: Hyper-Text Transport Protocal

Acronym: IP
Term: Internet Protocol
Definition: the predominant L3 protocol used in modern networks and the Internet
Other fields (not shown on cards):
Additional Info: Version 4 uses 32-bit addresses while version 6 uses 128-bit addresses

Q: SMTP
A: Simple Mail Transport Protocol

Q: PPP
A: Point-to-Point Protocol

Q: POP3
A: Post Office Protocal, Version 3

Acronym: MAC
Term: Media Access Control
Definition: The L2 address used by the Ethernet protocol
Other fields (not shown on cards):
Additional Info: The first three bytes (OUI) identify the manufacturer of the device, while the last three are a unique ID for the device itself

Acronym: CAM
Term: Content Addressable Memory
Definition: a type of memory used in network devices that allows memory addresses to be looked-up using some portion of their contents
Other fields (not shown on cards):
Additional Info: For example, a route stored in CAM could be retrievable by its prefix in addition to its location.

Q: What are the three main CLI modes of Cisco devices?
A: - User Mode
- Privileged or Enable Mode
- Configuration Mode

Purpose: move from User to Enable mode
Command: enable
Command Mode: user

Purpose: move from Enable to User mode
Command: disable
Command Mode: enable

Purpose: move from Enable to Configuration mode
Command: configure terminal
Command Mode: enable

Purpose: move from Configuration to Enable mode
Command: end
Command Mode: configuration

Q: What OSI layer is Ethernet an example of?
A: Layers 1 & 2

Q: What OSI layer is HTTP an example of?
A: Layer 5: Application

Q: What OSI layer is IP an example of?
A: Layer 3: Network

Q: What OSI layer is UDP an example of?
A: Layer 4: Transport

Q: What OSI layer is SMTP an example of?
A: Layer 5: Application

Q: What OSI layer is TCP an example of?
A: Layer 4: Transport

Q: What OSI layer is PPP an example of?
A: Layer 2: Data Link

Q: What OSI layer is T1 an example of?
A: Layer 2: Data Link

Q: What OSI layer is Telnet an example of?
A: Layer 5: Application

Q: What OSI layer is HDLC an example of?
A: Layer 2: Data Link

Q: Name three methods to connect to and configure a Cisco device
A: Console cable
Telnet
SSH

Q: Name three common interfaces used to connect between a computer and a Cisco console port
A: - Serial port to RJ-45 console using rollover cable
- USB port to RJ-45 console using USB converter and rollover cable
- USB port to USB console using USB cable

Q: What are the default serial parameters used by Cisco console ports?
A: - 9.6 kbaud (9600 bits/second)
- No flow control
- 8 data bits
- No parity
- 1 stop bit

Purpose: restart the device
Command: reload
Command Mode: enable

Purpose: set an encrypted password for entering enable mode
Command: enable secret
Command Arguments: <i>password</i>
Command Mode: configuration

Purpose: perform enable mode commands from configuration mode
Command: do
Command Mode: configuration

Term: OSI Session Layer
Definition: methods to group multiple bidirectional messages into a workflow
Other fields (not shown on cards):
Additional Info: Commonly includes transactional controls

Q: What are the four common types of memory found in a Cisco device?
A: - Random-Access Memory (RAM) running-config
- Read-Only Memory (ROM)
- Non-Volitile RAM (NVRAM) - startup-config
- Flash - IOS software image

Acronym: RAM
Term: Random-Access Memory
Definition: memory used to store the currently-running configuration and settings which will be lost or reset upon the next reboot
Other fields (not shown on cards):
Additional Info: RAM provides speed at the expense of data longevity

Acronym: ROM
Term: Read-Only Memory
Definition: memory used to store bootloader and firmware code use to startup the device
Other fields (not shown on cards):
Additional Info: ROM is used to protect essential operating code

Acronym: NVRAM
Term: Non-Volitile RAM
Definition: memory used to save the startup configuration
Other fields (not shown on cards):
Additional Info: NVRAM provides a compromise between RAM's performance and ROM's retention

Term: Flash
Definition: memory used to store IOS images
Other fields (not shown on cards):
Additional Info: Flash provides great capacity and read performance at the expense of power and write speeds

Purpose: copies the configuration from RAM into NVRAM
Command: copy running-config startup-config
Command Mode: enable

Purpose: move directly to enable mode
Command: Ctrl+Z
Command Mode: any

Acronym: UTP
Term: Unshielded Twisted-Pair
Definition: copper cable containing one or more pairs of wires which are twisted together
Other fields (not shown on cards):
Additional Info: The twising of pairs reduces pair-to-pair EMI or crosstalk

Q: STP (Cabling)
A: Shielded Twisted-Pair

Acronym: IEEE
Term: International Electrical and Electronics Engineers
Definition: the organization which creates and manages the standards for Ethernet and Wireless networks
Other fields (not shown on cards):
Additional Info: The IEEE is predominantly involved in L1 and L2 protocols

Term: RJ-45
Definition: the 8-pin connector format used for copper Ethernet cables and ports
Other fields (not shown on cards):
Additional Info: Technically only the port is called an RJ-45, the plug is part of the ITU's 8p8c standard

Acronym: NIC
Term: Network Interface Card
Definition: a computer component that provides a method to connect to a network
Other fields (not shown on cards):
Additional Info: NICs can be wired (Ethernet) or wireless

Acronym: SFP
Term: Small Form-Factor Pluggable
Definition: a standard which allows for the connection of different port types to the same logical interface
Other fields (not shown on cards):
Additional Info: Fiber Ethernet encompasses a large number of connectors and fiber types, so SFP and other technologies provide a low-cost way for networking devices to work with all these differnt formats

Q: Which wires are used for what purpose in 10 and 100 MBps Ethernet copper cables?
A: - Wire pair 1/2 for transmission (Tx)
- Wire pair 3/6 for reception (Rx)

Q: What is the difference between a Straight-Through and Crossover cable?
A: A crossover cable has pair 1/2 on one end connected to pair 3/6 on the other

Q: What three common network devices transmit on pins 1&2?
A: - NICs (hosts or computers)
- Routers
- Wireless Access Points

Q: What two common network devices transmit on pins 3&6?
A: - Hubs
- Switches

Q: What is the major difference (aside from speed) between 100BASE-T and 1000BASE-T?
A: Gigabit over copper (1000BASE-T) also uses pairs 4/5 and 7/8 on the cable

Q: What are the fields and sizes (in order) of the common Ethernet frame?
A: 1. Preamble, 7 bytes
2. Start Frame Delimiter (SFD), 1 byte
3. Destination Address, 6 bytes
4. Source Address, 6 bytes
5. Data, 46-1500 bytes
6. Frame Check Sequence (FCS), 4 bytes

Acronym: FCS
Term: Frame Check Sequence
Definition: provides data used to verify the integrity of an Ethernet frame

Q: SFD
A: Start Frame Delimiter

Q: What is the largest data payload an Ethernet frame can encapsulate?
A: 1500 bytes (1.5 kB)

Q: What is the smallest data payload an Ethernet frame can encapsulate?
A: 46 bytes

Acronym: MTU
Term: Maximum Transmission Unit
Definition: largest L3 payload that can be placed in an Ethernet frame

Acronym: OUI
Term: Organizationally Unique Identifier
Definition: portion of the MAC address which identifies the manufacturer of the interface
Other fields (not shown on cards):
Additional Info: The OUI is 3 bytes long and makes up the first 24 bits of the MAC address

Q: What is the length and organization of a MAC address?
A: 6 bytes (48 bits) long
- 3 byte OUI identified the manufacturer
- 3 byte unique value

Q: BIA
A: Burned-In Address

Term: Broadcast Address
Definition: a special value which is used to send data to all possible recipients

Term: Multicast Address
Definition: a special value which is used to send data to a subset of possible recipients

Q: What is the value of the MAC broadcast address?
A: FFFF.FFFF.FFFF

Term: Unicast Address
Definition: a special value which is used to send data to one specific recipient
Other fields (not shown on cards):
Additional Info: Most addresses in a TCP/IP network will be unicast

Q: What is the purpose of the Ethernet Type field?
A: To identify which protocol's information is contained in the Data field

Q: What is the Ethernet Type value used for IPv4 payloads?
A: 0x0800

Q: What is the Ethernet Type value used for IPv6 payloads?
A: 0x86DD

Term: Full-Duplex
Definition: an interface which can send and recieve at the same time

Term: Half-Duplex
Definition: an interface which must wait until after receiving to send data

Term: Hub
Definition: a generic device which operates at layer 1 of the networking model

Term: Switch
Definition: a generic device which operates at layer 2 of the networking model

Term: Router
Definition: A networking device that forwards packets between different networks or LANs
Other fields (not shown on cards):
Additional Info: a generic device which operates at layer 3 of the networking model

Acronym: CSMA/CD
Term: Carrier-Sense Multiple-Access with Collision Detection
Definition: Ethernet algorithm to detect and recovery from half-duplex collisions

Q: Describe the CSMA/CD process
A: 1. Listen until the line is free before sending
2. Listen for a collision while sending
3. If a collision is detected send a jamming signal to alert other devices
4. Wait a random amount of time before retrying a failed transmission

Q: What are the primary reasons for half-duplex connections in a network?
A: - The presence of half-duplex-only devices, such as Hubs
- Links which have failed auto-negotiation

Q: Name the major differences between a LAN and a WAN
A: - LANs connect local devices, while WANs connect distant devices
- WAN infrastructure is leased while LAN infrastructure is owned

Term: Leased Line
Definition: a connection whose user does not own the link, but instead rents the use of some or all of it

Acronym: CPE
Term: Customer Premises Equipment
Definition: devices located at the end of a leased line which provide the connection to that line

Acronym: CSU/DSU
Term: Channel Service Unit / Data Service Unit
Definition: an interface between a generic serial port and a specific leased line technology

Acronym: DTE
Term: Data Terminal Equipment
Definition: a cable which is used on the customer side of a leased line interface
Other fields (not shown on cards):
Additional Info: A DTE is typically straight-through and has a male connector

Acronym: DCE
Term: Data Communications Equipment
Definition: a cable which is used on the provider side of a leased line interface
Other fields (not shown on cards):
Additional Info: A DCE is typically crossover and has a female connector

Acronym: HDLC
Term: High-Level Data Link Control
Definition: a protocol used for L1 point-to-point links

Q: Name two common leased-line L1 protocols
A: - HDLC
- PPP

Q: What is the difference between the ISO and Cisco versions of HDLC?
A: Cisco adds the Type field to identify the protocol contained in the Data field

Q: MPLS
A: Multi-Protocol Label Switching

Q: CATV
A: Cable TV

Q: DSL
A: Digital Subscriber Line

Q: CO
A: Central Office

Q: SP
A: Service Provider

Q: DSLAM
A: DLS Access Multiplexer

Q: Describe how a DSL connection is typically made
A: The PSTN is used to connect a DSL modem on the customer's end to a DSLAM located in the Telco CO, both connect to the respective networks on each end

Q: Describe how a Cable connection is made
A: The CATV link is used to connect a Cable modem on the customer's end to a broadband router located in the cable company's office, both connect to the respective networks on each end

Q: PSTN
A: Public Switched Telephone Network

Q: Leased lines are commonly found in multiples of what two speeds?
A: - 64 kbps
- 1.5 Mbps

Q: How large is an IPv4 Address?
A: 32 bits, usually displayed as four decimal octets

Q: Two hosts are connected to seperate interfaces on the same router; describe the process all devices go through in order for host A to send a packet to host B
A: - Host A: compares destination IP to own subnet
- Host A: ARPs for default gateway
- Router: Responds to Host A ARP with MAC
- Host A: Encapsulates packet in Frame destined to Router's MAC and transmits
- Router: Checks destination MAC, deencapsulates, checks destination IP
- Router: Destination IP is local, ARPs for destination MAC
- Host B: Responds to Router ARP with MAC
- Router: Encapsulates packet in Frame destined to Host A's MAC and transmits
- Host B: Checks destination MAC, deencapsulates, checks destination IP
- Host B: Recieved packet

Q: Two hosts are connected via a switch to the same interface on a router; describe the process all devices go through in order for host A to send a packet to host B
A: - Host A: compares destination IP to own subnet
- Host A: ARPs for destination MAC
- Host B: Responds to ARP with MAC
- Host A: Encapsulates packet in Frame destined to Host A's MAC and transmits
- Host B: Checks destination MAC, deencapsulates, checks destination IP
- Host B: Recieved packet

Q: Hosts seperated by a router must be in different what?
A: IP Subnets

Q: Describe all the IPv4 address ranges, their purpose, and class
A: First Octet | Purpose and Class
0 | Reserved
1-126 | Class A, Unicast
127 | Reserved, Loopback
128-191 | Class B, Unicast
192-223 | Class C, Unicast
224-239 | Class D, Multicast
240-255 | Class E, Reseved, Experimental

Q: List the default subnet masks of the three primary IPv4 address classes
A: A: 255.0.0.0
B: 255.255.0.0
C: 255.255.255.0

Q: List the goals of a routing protocol
A: 1. Learn paths to all available subnets
2. Chose the best paths to each available subnet
3. Place the best routes into the route table
4. Remove routes when they are no longer valid
5. Prevent routing in a loop

Q: Describe the purpose and process of the DNS protocol
A: Allows the discovery of IP Addresses based on Domain Name.
- Host sends a DNS request containing the Domain Name to the Server
- Server responds with a DNS response containing the IP Address to the Host

Q: Describe the purpose and process of the ARP protocol
A: Allows the discovery of MAC Addresses based on IP Address
- Host broadcasts an ARP Request containing the target IP Address to all local Hosts
- Owner unicasts an ARP Response containing their MAC Address

Acronym: MPLS
Term: Multiprotocol Label Switching
Definition: A WAN technology used internally by service providers
Other fields (not shown on cards):
Additional Info: MPLS adds a label at the network edge so that routing table lookups only need to happen once which reduces router CPU load.

Acronym: EoMPLS
Term: Ethernet over MPLS
Definition: A MPLS service which provides an Ethernet handoff on the customer ends

Q: From a networking perspective, what is the Internet?
A: A large, interconnected collection of TCP/IP networks.

Q: What is the purpose of the IP Subnet Mask?
A: Differentiates between addresses which are local (match the mask) and can be sent directly to the host, and addresses which are remote (do not match) and must be sent through a router to reach the destination.

Q: Define 6 Characteristics of TCP
A: - Operates at transport layer of TCP/IP stack (OSI Layer 4)
- Error recovery through checksum and retransmissions
- Flow control
- Operates in full-duplex mode
- Ordered transmission of segmented data
- Reliable (Connection-Oriented)

Term: Multiplexing (Transport Layer)
Definition: identifying data meant for different applications on the same host using port numbers

Q: What information identifies a TCP or UCP session?
A: 1. Source IP
2. Source Port
3. Destination IP
4. Destination Port

Q: What are the two ranges of TCP/UDP Port numbers?
A: 0-1024: Well-known applications
1025+: Dynamically assigned

Term: Socket
Definition: a combination of an IP Address, Transport Protocol, and Port number that identify a connection
Other fields (not shown on cards):
Additional Info: Two sockets on different hosts make up a TCP or UDP Session

Port: 21
Protocol: TCP
Application: FTP Control
Additional Info: FTP uses two sockets, one for data and one for control information

Port: 22
Protocol: TCP
Application: SSH

Port: 23
Protocol: TCP
Application: Telnet

Port: 25
Protocol: TCP
Application: SMTP

Port: 53
Protocol: UDP
Application: DNS
Additional Info: DNS uses UDP for server-to-host and TCP for server-to-server connections

Port: 67
Protocol: UDP
Application: DHCP Server

Port: 68
Protocol: UDP
Application: DHCP Client

Port: 80
Protocol: TCP
Application: HTTP

Port: 110
Protocol: TCP
Application: POP3

Port: 161
Protocol: UDP
Application: SNMP

Port: 443
Protocol: TCP
Application: SSL (Secure HTTP)

Port: 514
Protocol: UDP
Application: Syslog

Term: 3-Way Handshake
Definition: how TCP establishes a connection

Q: Describe the 3-Way Handshake process
A: - Request sent with SYN flag
- Reply sent with SYN and ACK flags
- Confirmation sent with ACK flag
These messages are commonly known as SYN, SYN/ACK, and ACK respectively

Q: Describe the TCP termination process
A: - Host A sends request with ACK and FIN flags set
- Host B responds with ACK flag set
- Host B sends request with ACK and FIN flags set
- Host A confirms with ACK flag set

Term: Connection-Oriented Protocol
Definition: a protocol that requires an exchange before data transfer begins

Term: Connectionless Protocol
Definition: a protocol which can send data immediately

Q: Describe how TCP error recovery works
A: The recipient acknowledges the number of continguous bytes recieved which allows the sender to continue or to re-send lost data

Q: Describe how TCP windowing works
A: The recipient can give the sender a window which determines how many bytes it may send before waiting for an acknowledgement

Q: Explain how the recipient of an Ethernet frame determines which application gets the encapsulated HTTP data?
A: - Ethernet Type field identifies the L3 protocol
- IP Protocol field identifies the L4 protocol
- TCP Port Number identifies the L5 protocol
- HTTP data is delivered to the application

Q: List the two primary Cisco configurations, their purpose, and where they are stored
A: - Startup config, saved configuration that will be loaded after a reboot, stored in NVRAM
- Running config, current operating mode including changes from the startup config, stored in RAM

Q: List three ways to erase the startup configuration
A: - write erase
- erase startup-config
- erase nvram:

Q: What Ethernet field do switches use to populate their MAC table?
A: Source Address

Acronym: STP (Protocol)
Term: Spanning-Tree Protocol
Definition: a protocol used to eliminate Layer 2 loops

Q: What logic do switches use to decide where to forward frames?
A: - Unicast destinations that are found in the MAC table are sent out the learned port, if that port is different than the arrival port
- All other traffic (Broadcast and Unknown Unicast) are sent out all ports, except the arrival port

Purpose: list all a switch's Ethernet addresses
Command: show mac address-table
Command Mode: exec

Purpose: remove all VLAN details from a switch
Command: delete vlan.dat
Command Mode: exec

Purpose: set a device's name
Command: hostname name
Command Mode: exec

Purpose: show the connection state of a switch's ports
Command: show interfaces status
Command Mode: exec

Purpose: show the connection state of a single switch ports
Command: show interfaces int-id status
Command Mode: exec

Purpose: show the details of a single switch ports
Command: show interfaces int-id
Command Mode: exec

Purpose: show the packet statistics for a single switch port
Command: show interfaces int-id counters
Command Mode: exec

Purpose: list a swtich's learned Ethernet addresses
Command: show mac address-table dynamic
Command Mode: exec

Purpose: show specific entry from a switch's learned Ethernet addresses
Command: show mac address-table dynamic address mac-address
Command Mode: exec

Purpose: show entries from a switch's Ethernet addresses learned on a specific port
Command: show mac address-table dynamic interface int-id
Command Mode: exec

Purpose: show entries from a switch's Ethernet addresses related to a specific vlan
Command: show mac address-table dynamic vlan id
Command Mode: exec

Term: Aging Time
Definition: the length of time a MAC address stays in a table without any matching source traffic

Q: What is the default Aging Time for most switches?
A: 300 seconds (5 minutes)

Purpose: show how long unused Ethernet addresses are remembered
Command: show mac address-table aging-time
Command Mode: exec

Purpose: summarize how many addresses are in a switch's CAM table
Command: show mac address-table count
Command Mode: exec

Purpose: forget all learned Ethernet addresses
Command: clear mac address-table dynamic
Command Mode: exec

Q: What is the difference between the `enable secret` and `enable password` commands?
A: Enable secret encrypts the provided password in the config so that it cannot be looked up or accidentally shared

Q: When is the console configuration used compared to the vty configuration?
A: The console config is only used for physical connections via the console port. All network connections (using SSH or Telnet) use the vty configuration.

Purpose: enable simple password protection for a line connection
Command: login
Command Mode: line configuration

Purpose: provide the correct password for a line connection
Command: password
Command Mode: line configuration

Purpose: enter configuration mode for physical connections
Command: line console 0
Command Mode: configuration

Purpose: enter configuration mode for network connections
Command: line console vty start end
Command Mode: configuration

Purpose: enable username-based password protection for a line connection
Command: login local
Command Mode: line configuration

Q: simple password protection for line connections
A: - Enter line configuration mode
- Set a password
- Require a login

Purpose: save a username / password combination
Command: username username secret password
Command Arguments: privilege level
Command Mode: configuration

Q: What are the best practices for securing a Cisco device?
A: - Use username/password authentication
- Remove line passwords
- Disable Telnet connections
- Specify SSH and Console timeouts
- Use a discouraging banner

Q: AAA
A: Authenticaion, Authorization, and Accounting

Q: List the two common AAA protocols
A: - RADIUS
- TACACS+

Q: What is the purpose of an AAA server?
A: Provides centralized AAA services that keep settings consistent across devices

Q: SSH network connections
A: - Set the hostname
- Set the domain name
- Generate a keypair
- Add local users
- Set the SSH version

Purpose: set the device's domain name
Command: ip domain-name domain
Command Mode: configuration

Purpose: generate a keypair
Command: crypto key generate rsa
Command Arguments: modulus length
Command Mode: configuration

Purpose: set which type of network line connections are allowed
Command: transport input [all|none|telnet|ssh]
Command Mode: line configuration

Purpose: show secure shell server details
Command: show ip ssh
Command Mode: exec

Purpose: show secure shell connection details
Command: show ssh
Command Mode: exec

Acronym: IOS
Term: Internetwork Operating System
Definition: The OS which runs Cisco routers and switches

Acronym: SVI
Term: Switched Virtual Interface
Definition: A virtual interface associated with a VLAN
Other fields (not shown on cards):
Additional Info: SVIs act (mostly) like physical interfaces except for not being physical devices

Purpose: configure an SVI
Command: interface vlan vlan-id
Command Mode: configuration

Purpose: set an ipv4 address on a port
Command: ip address address netmask
Command Mode: interface configuration

Purpose: enable or disable an interface
Command: [no] shutdown
Command Mode: interface configuration

Purpose: set the secure shell version
Command: ip ssh version ver
Command Mode: configuration

Q: What is the minimum keylength for SSH version 2?
A: 768 bits

Acronym: DHCP
Term: Dynamic Host Configuration Protocol
Definition: protocol used to provide hosts with IP configuration details

Q: What is the purpose of an IP default gateway?
A: Provides a destination for hosts outside of the local subnet; provides routing to the rest of the reachable IP address space

Purpose: set a switch's control planet default first-hop
Command: ip default-gateway ip-address
Command Mode: configuration

Q: What is the difference between a default gateway and a default route?
A: - The default route is used by the data plane, e.g. packet routing
- The default gateway is used by the management plane, e.g. utilities like ping and traceroute

Purpose: set a switch's control plane dns servers
Command: ip name-server ip-address [ip-address...]
Command Mode: configuration

Q: an SVI
A: - Enter configuration mode
- Set the default gateway
- Optionally, set the DNS server addresses
- Enter vlan interface configuration mode
- Set the interface IP address
- Enable the interface

Purpose: enable DHCP on a port
Command: ip address dhcp
Command Mode: interface configuration

Purpose: show interface DHCP timers and details
Command: show dhcp lease
Command Mode: exec

Purpose: show past configuration commands
Command: show history
Command Mode: exec

Purpose: set how many commands to remember for this session
Command: terminal history size length
Command Mode: exec

Purpose: set how many commands to remember by default
Command: history size length
Command Mode: exec

Purpose: disable or enable log messages appearing on the command line
Command: [no] logging console
Command Mode: configuration

Purpose: do not show messages while entering a command
Command: logging synchronous
Command Mode: line configuration

Purpose: disable DNS requests for unknown addresses
Command: no ip domain-lookup
Command Mode: configuration

Purpose: set the communication bandwidth of an Ethernet interface
Command: speed [auto|speed]
Command Mode: interface configuration

Purpose: set the duplex mode of an interface
Command: duplex [auto|full|half]
Command Mode: interface configuration

Purpose: add some identifying text to an interface
Command: description description
Command Mode: interface configuration

Purpose: configure an interface
Command: interface int-id
Command Mode: configuration

Q: What speed and duplex does an Ethernet interface use when autonegotiation fails?
A: - Slowest speed
- If the slowest speed is 100 Mbps or slower, use half duplex
- If the slowest speed is 1 Gbps or faster, use full duplex

Q: What is the difference between IEEE and Cisco autonegotiation?
A: IEEE autonegotiation fails to slowest speed, Cisco attempts to detect the speed outside of autonegotiation

Q: What will be the resulting link speed if a 10/100 port manually configured to 100/Full is connected to a Cisco 10/100/1000 port with autonegotiation enabled?
A: The 10/100 port will transmit at 100 Mbps / full duplex while the gigabit port will fail to half duplex but detect the 100 Mbps speed resulting in a duplex mismatch

Q: What is the most obvious symptom of a duplex mismatch?
A: Large number of collisions resulting in a transmit speed below that of a half-duplex connection

Term: Port Security
Definition: a Cisco technology can be used to limit the number of devices that can connect to a switchport

Purpose: enable MAC address limiting on an interface
Command: switchport port-security
Command Mode: interface configuration

Q: What are the default port security settings?
A: - Violation mode: shutdown
- Maximum addresses: 1
- Sticky: disabled
- Aging: disabled

Purpose: set the maximum number of unique Ethernet addresses that can use an interface
Command: switchport port-security maximum number
Command Mode: interface configuration

Purpose: set the action to be taken when too many Ethernet addresses use an interface
Command: switchport port-security violation [protect|restrict|shutdown]
Command Mode: interface configuration

Purpose: save an interface's learned Ethernet addresses to the running config
Command: switchport port-security mac-address sticky
Command Mode: interface configuration

Purpose: pre-define an allowed Ethernet address for an interface
Command: switchport port-security mac-address mac-address
Command Mode: interface configuration

Q: port security on an interface
A: - Enter interface configuration mode
- Set the interface mode to Access or Trunk
- Enable port security
- Set the violation mode
- Optionally, change the maximum number of addresses
- Optionally, enable sticky learning
- Optionally, add pre-defined addresses

Q: What are the violation modes for port security and their differences?
A: Protect: drops traffic
Restrict: drops traffic, logs & counts the event
Shutdown: drops traffic, logs & counts the event, disables the interface

Q: What are the differences between a sticky and non-sticky learned port security MAC address?
A: - Sticky-learned addresses are saved to the running config
- Sticky-learned addresses do not age out of the table

Purpose: list all the Ethernet addresses learned via port security
Command: show mac address-table secure
Command Mode: exec

Purpose: list all the Ethernet addresses learned on an interface via port security
Command: show mac address-table secure interface int-id
Command Mode: exec

Purpose: list all the predefined or port security Ethernet addresses
Command: show mac address-table static
Command Mode: exec

Purpose: show a summary of port security counters
Command: show port-security
Command Mode: exec

Purpose: show port security settings for an interface
Command: show port-security interface int-id
Command Mode: exec

Purpose: set the operation mode of a switchport
Command: switchport mode [dynamic auto|dynamic desirable|access|trunk]
Command Mode: interface configuration

Q: In the most general sense, how many collision domains does an 8-port hub have?
A: One, a hub always has a single collision domain

Q: In the most general sense, how many broadcast domains does an 8-port hub have?
A: One, a hub always has a single broadcast domain

Q: In the most general sense, how many collision domains does a 12-port switch have?
A: Twelve, one for each port

Q: In the most general sense, how many broadcast domains does a 12-port switch have?
A: One, a unconfigured switch always has a single broadcast domain

Q: In the most general sense, how many broadcast domains does a 4-port router have?
A: Four, one for each port

Q: In the most general sense, how many collision domains does a 4-port router have?
A: Four, one for each port

Q: Describe the differences between a Hub, a Bridge, and a Switch
A: - A hub has a single collision domain shared with all ports
- A bridge has a seperate collision domain for each port, but does not learn MAC addresses
- A switch has a seperate collision domain for each port, and learns MAC addresses so traffic only exits the port of its destination

Q: In the most general sense, how many broadcast domains does a 12-port switch have where half the ports are in VLAN1 and the other half in VLAN2?
A: Two, one for each VLAN

Term: Access Layer
Definition: switches which connect directly to end users and hosts

Term: Distribution Layer
Definition: switches which connect the access switches at a site together and redundantly to the core switches

Term: Core Layer
Definition: switches which connect all site distribution layers together along with other specialized network segments

Q: What is the purpose of a tiered campus design?
A: Reducing interconnects by connecting a group of switches to a central point instead of each other

Term: Two-Tier Campus Design
Definition: a topology where the distribution and core roles are served by the same devices
Other fields (not shown on cards):
Additional Info: Suitable for smaller networks, and can be easily expanded to a three-tier design

Term: Three-Tier Campus Design
Definition: a topology where the access, core, and distribution layers are all on seperate devices
Other fields (not shown on cards):
Additional Info: For larger networks, each site only needs to connect to the core instead of all other sites

Term: Star Topology
Definition: an organizational structure where a central device connects to several others, while those other devices only connect to the central device

Term: Full Mesh Topology
Definition: an organizational structure where each device is connected directly to all other devices

Term: Partial Mesh Topology
Definition: an organizational structure where devices connect to many other devices, but not all

Term: Hybrid Topology
Definition: an organizational structure that combines features of star and mesh topologies

Q: What TIA cable is required for 100 m 10BASE-T Ethernet?
A: TIA CAT3 or better with 2 pairs

Q: What TIA cable is required for 100 m 100BASE-T Ethernet?
A: TIA CAT5 UTP or better with 2 pairs

Q: What TIA cable is required for 100 m 1000BASE-T Ethernet?
A: TIA CAT5e UTP or better with 4 pairs

Q: What TIA cable is required for 100 m 10GBASE-T Ethernet?
A: TIA CAT6a UTP or better with 4 pairs

Q: What TIA cable is required for 55 m 10GBASE-T Ethernet?
A: TIA CAT6 UTP or better with 4 pairs

Acronym: TIA
Term: Telecommunications Industry Association
Definition: Defines Ethernet cabling standards

Acronym: VTP
Term: VLAN Trunking Protocol
Definition: a protocol used to share VLAN information between switches

Acronym: DTP
Term: Dynamic Trunking Protocol
Definition: a protocol used to negotiate trunking between devices

Purpose: verify the Cisco IOS version and release numbers of the IOS Software that is running on a Cisco switch
Command: show version
Command Mode: privileged exec

Purpose: displays the current running (active) configuration file of the switch.
Command: show running-config
Command Arguments: [int] [all]
Command Mode: pivileged exec

Purpose: command displays the status and statistical information for the network interfaces
Command: show interfaces
Command Arguments: int name
Command Mode: privilege exec

Q: What are straight-through cables and crossover cables used for?
A: Straight-through connect unlike devices
SW-RT
SW-PC
Crossover cables are used for connecting like devices. PC-PC
SW-HUB

Q: What is MMF and its characteristics?
A: Multimode Fiber, used on shorter distances at a lower bit rate and cheaper than SMF

Q: What is SMF and its characteristics?
A: Single Mode Fiber, used on longer distances at a faster bit rate and more expensive than MMF

Q: List 6 troubleshooting methods
A: 1. Top-down method
2. Bottom-up method
3. Divide-and-conquer method
4. Perform comparison method
5. Follow-the-path method
6. Swap components method

Q: RTT
A: Round-Trip Time. Time required for a network communication to travel from the source to the destination and back

Q: What are 7 characteristics of IP?
A: Connectionless protocol
Packets treated independently
Hierarchical addressing
Best-effort delivery
No data-recovery features
Media-independent
IPv4 or IPv6

Q: Name the 14 IPv4 Header Fields
A: Source Address
Destiination Address
Version: IP version
IHL: Lenght of the header
Service Type: Quality of service
Total Length: Length of packet including header and data
Identification: Used for unique fragment identifcation
Flag: Control flags for fragmentation
TTL: Time to live of packet
Protocol: Protocol of data in packet
Header Checksum: Error detection of ip header
Options: Optional parameters
Padding: Used to end header at 32-bit boundary

Term: Network Address
Definition: Standard way to refer to a network
Other fields (not shown on cards):
Additional Info: Seperated into classes A-E

Term: Local Broadcast Address
Definition: All numbers set to one. (255.255.255.255)
Other fields (not shown on cards):
Additional Info: Never routed beyond the local network

Term: Directed Broadcast Address
Definition: Allows communication to all hosts in network. Eg 172.16.255.255
Other fields (not shown on cards):
Additional Info: Directed breadcast can be routed over internet. Disabled by default on Cisco

Term: Network ID
Definition: Network portion of an IP address
Other fields (not shown on cards):
Additional Info: EG [172.16].0.0

Q: What are the 3 classes of private ip addresses and their ranges?
A: A = 10.0.0.0 to 10.255.255.255
B = 172.16.0.0 to 172.31.255.255
C = 192.168.0.0 to 192.168.255.255

Q: What are the 3 classes of public ip addresses and their ranges?
A: A = 1.0.0.0 to 9.255.255.255
      (10.0.0.0 to 10.255.255.255)
      11.0.0.0 to 126.255.255.255
B = 128.0.0.0 to 172.15.255.255
       (172.16.0.0 - 172.31.255.255)
       172.32.0.0 to 191.255.255
C = 192.0.0.0 to 192.167.255.255
       (192.168.0.0 to 192.168.255.255)
       192.169.0.0. to 223.255.255.255

Acronym: VLSM
Term: Variable-length subnet mask
Definition: Capability to specify a different subnet mask for the same network number on different subnets.
Other fields (not shown on cards):
Additional Info: Helps optimize availabe address space

Term: Broadcast Domain
Definition: Network which all devices can reach each other by broadcast

Term: Subnet Mask
Definition: 32 bit binary number that is used to define which portion of an ip address is the subnet and which portion of an ip address refers to the host

Q: What is the MTU of IP protocol
A: 1500 bytes (larger is possible)

Term: Segmentation
Definition: The process of splitting data in to chunks in the Transport layer.

Q: What is the difference between TCP and UDP with regards to Segmentation
A: TCP handles segmentation independent of the application
UDP relies on the application to handle segmentation

Q: Define 4 Characteristics of UDP
A: - Operates at transport layer of TCP/IP stack (OSI Layer 4)
- Provides speed and low-overhead data over reliability
- Uses a best effort approach, with no guarantee data delivery
- Connectionless protocol

Q: Give 7 examples of applications that use UDP
A: -DNS
-Streaming Video
-VoIP
-TFTP
-SNMP
-DHCP
-RIP

Purpose: viewing open ports
Command: show contol-plane host open-ports
Command Mode: en

Q: What are the 4 major hardware components of a router?
A: -CPU
-Motherboard
-Memory
-Ports

Q: What type of ports are typically found on a router
A: Management Ports
-Ethernet Management Port
-AUX Port (Dialer)
-Console Port
Network Ports

Q: What are a router's two main functions?
A: -Path determination: Use of routing tables to determinte where to forward packets
-Packet forwarding: Transmission of data

Term: Routing Table
Definition: Table stored in a router that keeps track of routes to particular network destinations
Other fields (not shown on cards):
Additional Info: Can also store metrics associated with those routes

Q: What type of entries are kept in a routing table
A: Directly connected: Connected to interface on local router, automatically added
Static routes: Manually configured routes
Default routes: Optional entry used when no explicit parth to destination is found
Dynamic routes: Automatically added when routing protocol is configured

Purpose: Show contents of routing table
Command: show ip route
Command Mode: en

Q: What are four commonly used routing metrics
A: Bandwith: data capacity of a link
Delay: Time required to move a packet along each link
Cost: Arbitrary value that an administrator assigns
Hop Count: Number of routers that a packet must travel through

Term: Administrative Distance
Definition: Rating fo the trustworthiness of a routing information source. Expressed as a numerical value between 0 and 255. Lower number means more trustworthy. The protocol with lowest administrative distance is installed into the routing table.
Other fields (not shown on cards):
Additional Info: Cisco will give it's own protocols a lower value (more trustworthy)
Examples
Direct = 0
Static = 1
EIGRP = 90

Q: What types of general physical interfaces are on cisco routers
A: Ethernet interfaces
-interface ethernet 10 Mbps
-interface fastethernet 100 Mbs
-interface gigabitethernet 1000 Mbs 1Gbs
Serial interfaces (leased lines and Frame Relay)
-interface serial

Q: Configure interface
A: conf t
interface <interface type> <number>
ip address <ip-address> <mask>
no shutdown
exit

Q: Define Cisco Interface Status Codes
A: Line status: first code, refers to layer 1 status
Protocol status: second code, generally refers to layer 2 status, mismatched data link layer configuration causes "down" status

Q: Troubleshoot Interface Status Codes
A: administratively down, down : interface has shutdown applied
down, down : physical layer problem
up, down : data link layer problem
up, up : functional

Q: What is the cisco protocol to find information about the network topology?
A: Cisco Discovery Protocol

Acronym: LLDP
Term: Link Layer Discovery Protocol
Definition: Standardized, ventor-independent protocol for finding different neighboring devices
Other fields (not shown on cards):
Additional Info: IEEE standardized protocol, cisco uses CDP

Purpose: view Cisco Discovery Protocol information
Command: show cdp
Command Mode: enabled

Purpose: disable or enable Cisco Discovery Protocol globally
Command: [no] cdp run
Command Mode: configuration

Purpose: enable or disable Cisco Discovery Protocol on an interface
Command: [no] cdp enable
Command Mode: configuration interface

Purpose: display information about CDP neighbors
Command: show cdp neighbors
Command Arguments: detail
Command Mode: enable

Purpose: enable or disable LLDP globally
Command: [no] lldp run
Command Mode: enable

Purpose: enable or disable LLDP on an interface
Command: [no] lldp transmit
[no] lldp receive
Command Mode: enable

Q: What are the two services that ARP provide
A: -Address Resolution: mapping an IP address to MAC address
-Caching: Storing MAC addresses learnt via ARP

Purpose: display ARP table
Command: show ip arp
Command Arguments: <ip-address> <host-name> <mac-address> <interface type number>
Command Mode: enable

Q: Troubleshoot IP Addressing
A: Ping loopback address on host
Ping local host
Ping default gateway
Ping the remote server

Q: Describe the Routing Methodology
A: Identify the destination address
Identify the sources of routing information
Identify routes
Select routes
Maintain and verify routing information

Term: Static Route
Definition: Manually configured route
Other fields (not shown on cards):
Additional Info: Use in small networks and hub-and-spoke topology and for quick ad hoc situations
Advantages
- Conserve router resources
- Simple to configure
- Secure
Disadvantages
- Scalability
- Accuracy
- High maintenance

Term: Dynamic Route
Definition: Router dynamically learns routes through a protocol

Purpose: define a static route
Command: ip route
Command Arguments: <ip-address> <mask> <ip-address | interface>
Command Mode: configuration
Command Example: ip route Identifies the static route
0.0.0.0 Routes to networks that are not in the routing table
0.0.0.0 Special mask that indicates the default route
172.16.2.2 IP address fo the next-hop router to be used as the default for packet forwarding

Q: What are the formulas to calculate amount of Subnets and Hosts in an ip address and mask?
A: Subnet bits = 2^n
Host bits = 2^n - 2

Write out the Subnet and Mask Table