Title: ICND1 / 4. IP Routing Technologies

Q: The _____________ command is used to change the setting of the configuration register.
The _____________ has the boot field setting, which specifies the order in which the router should look for bootstrap information. The router contains a 16-bit software register, which is stored in the non-volatile random access memory (NVRAM).
The _____________ command is used to modify the default configuration register. The most common use of changing this register is to instruct the router to ignore the stored configuration file and boot as a new router with no configuration. This process is normally used when a router has a password that is not known and must be reset. For security purposes, this procedure can only be performed from the console connection, which means it requires physical access to the router.
A: config-register

Q: The __________ command causes a routing protocol to change its default behavior of discarding any traffic that is bound for unknown subnets of a known classful network. If the command is enabled, the router tries to match the most number of bits possible against the route in its routing table. Alternatively, the router will use the default route rather than dropping the packet.
A: ip classless

Q: The ____________ command is used to view (detailed) information about a specific neighboring device.
A: show cdp entry *
show cdp entry r1

Q: The __________ command is used to disable CDP on a Cisco router globally.
A: no cdp run

Q: The _____________ command is used to disable CDP on an interface. In a situation where CDP needs to be disabled on a single interface only, such as the interface leading to the Internet, this command would be executed from interface configuration mode for that specific interface. It will not disable the protocol globally.
A: no cdp enable
For example, to disable CDP for only the serial0 interface, the command sequence would be:
Router#configure terminal
Router(config)#interface serial 0
Router(config-if)no cdp enable

Q: Which Cisco IOS command is used to view the information about the interfaces on which Cisco Discovery Protocol (CDP) is enabled?
A: show cdp interface

Q: Router IDs are determined first by the ____________, followed by the highest IP address on an active physical interface.
A: highest loopback IP address

Q: Changing the priority to ____ would make the router ineligible to become the DR or the backup designated router (BDR).
A: 0

Q: ________ is a packet switching technology that allows a single WAN connection to host multiple virtual circuits. These circuits are identified by Layer 2 addresses called Data Link Connection Identifiers (DLCI).
A: Frame relay

Q: ____________ does not send data in fixed size calls. This is a characteristic of Asynchronous Transfer Mode (ATM).
____________ uses variable length packet sizes.
A: Frame relay

Q: Frame Relay is not an example of cell switching. Cell switching is a characteristic of ___________. Frame relay uses packet switching technology.
A: ATM

Q: ______________ is used to prevent routing loops in distance vector routing environments. It prevents a router from advertising a network back in the direction of the router from which it was learned. In this sense, route advertisements flow "downstream" (away from the route), but never "upstream" (back towards the advertised route).
A: Split horizon

Q: ______________ describes when a router learns that a network has gone down, and the router sends an update back to the neighbor with an infinite metric.
A: Poison reverse

Q: ________ describes when a router ignores any route advertisements that have a lower metric to a downed route.
A: Holddown

Q: _______ updates describe when a router immediately sends a route update with an infinite metric, as opposed to waiting for its next regularly scheduled routing update.
A: Triggered

Q: _________________________ are packets that are flooded when a topology change occurs, causing network routers to update their topological databases and recalculate routes.
A: Link State Advertisements (LSA)

Q: Which WAN switching technology is used with ISDN?
A: circuit switching

Q: Administrative Distance for RIP: ___
A: 120

Q: Administrative Distance for OSPF: ___
A: 110

Q: Administrative Distance for IGRP: ___
A: 100

Q: Administrative Distance for EIGRP: ___
A: 90

Q: Administrative Distance for BGP: ___
A: 20

Q: Administrative Distance for Static Route: ___
A: 1

Q: Administrative Distance for Directly Connected Interface: ___
A: 0

Q: What does the "bandwidth" interface subcommand do?
A: It tells the IOS what speed to assume the interface is using to assist with routing metrics.

Q: A router can take routes learned by OSPF and advertise them into EIGRP, and vice versa, through a process called _______________.
A: route redistribution

Q: What command produced this output?
-----------------------------------------------------------------------------------------
            OSPF Router with ID (10.10.13.2) (Process ID 1)
                Router Link States (Area 0)
Link ID         ADV Router      Age         Seq#       Checksum Link count
10.10.11.1      10.10.11.1      117         0x80000004 0x00fd83 2
10.10.13.1      10.10.13.1      65          0x80000004 0x002852 2
10.10.13.2      10.10.13.2      51          0x80000004 0x0076fa 2
10.10.12.2      10.10.12.2      51          0x80000004 0x002a4e 2
                Net Link States (Area 0)
Link ID         ADV Router      Age         Seq#       Checksum
10.10.10.1      10.10.13.1      167         0x80000001 0x00ee07
10.10.11.2      10.10.12.2      117         0x80000001 0x00b93d
10.10.13.2      10.10.13.2      65          0x80000001 0x003e55
10.10.12.2      10.10.13.2      51          0x80000002 0x00da13
-----------------------------------------------------------------------------------------
A: show ip ospf database

Q: Routers reflood an LSA when ___________________.
They also reflood each LSA based on __________________.
A: some information changes, for example, when a link goes up or comes down.
each LSA’s separate aging timer (default 30 minutes).

Q: OSPF Hello message follows the ___(protocol) packet header, with IP protocol type ___(#).
A: IP, 89

Q: Hello packets are sent to ___________________, a multicast IP address intended for all OSPF-speaking routers.
A: multicast IP address 224.0.0.5

Q: OSPF routers listen for packets sent to _____________________, in part hoping to receive Hello packets and learn about new neighbors.
A: IP multicast address 224.0.0.5

Q: What command produced the following
----------------------------------------------------------------------------------------------------
Neighbor ID     Pri   State           Dead Time   Address         Interface
10.10.12.2        1   FULL/BDR        00:00:33    10.10.12.1      FastEthernet0/0
10.10.13.1        1   FULL/BDR        00:00:37    10.10.13.1      FastEthernet0/1
----------------------------------------------------------------------------------------------------
A: show ip ospf neighboor

Q: What command produced the following output?
--------------------------------------------------------------------------
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route
Gateway of last resort is not set
     10.0.0.0/24 is subnetted, 4 subnets
O       10.10.10.0 [110/2] via 10.10.13.1, 00:44:47, FastEthernet0/1
O       10.10.11.0 [110/2] via 10.10.12.1, 00:44:33, FastEthernet0/0
C       10.10.12.0 is directly connected, FastEthernet0/0
C       10.10.13.0 is directly connected, FastEthernet0/1
-----------------------------------------------------------------------------------------------
A: show ip route

Q: What command produced the following output?
-------------------------------------------------------------------------------------
Routing Protocol is "ospf 1"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 10.10.13.2
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    0.0.0.0 255.255.255.255 area 0
  Routing Information Sources:
    Gateway         Distance      Last Update
    10.10.11.1           110      00:20:31
    10.10.12.2           110      00:19:25
    10.10.13.1           110      00:19:39
    10.10.13.2           110      00:19:25
  Distance: (default is 110)
-------------------------------------------------------------------------------------
A: show ip protocols

Q: Routers will automatically choose their Router ID by the following means:
1. If the ________ OSPF subcommand is configured, this value is used as the RID.
2. If any loopback interfaces have an IP address configured, and the interface has an interface
status of up, the router picks the _______ IP address among these loopback interfaces.
3. The router picks the _______ IP address from all other interfaces whose interface status
code (first status code) is up. (In other
A: "router-id [x.x.x.x]",
highest,
highest

Q: How do you restart the OSPF process?
A: clear ip ospf process

Q: How do you set an interface to passive mode, allowing OSPF to advertise about that site, but not send LSA TO the interface itself (an interface connecting to a switch/clients, for example)
A: passive-interface gigabitethernet0/1

Q: How would you be able to see which interfaces are set to passive mode (OSPF)
A: show ip ospf interface g0/0

Q: Which command produced the following output?
---------------------------------------------------------------------------
GigabitEthernet0/0 is up, line protocol is up
  Internet address is 10.10.12.1/24, Area 0
  Process ID 1, Router ID 10.10.12.2, Network Type BROADCAST, Cost: 1
  Transmit Delay is 1 sec, State WAITING, Priority 1
  No designated router on this network
  No backup designated router on this network
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    No Hellos (Passive interface)
  Index 2/2, 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: show ip ospf interface gi0/0

Q: How would you tell a router with a default route to the internet to advertise the default route, having all other routers point to that router?
A: configure terminal
ip route 0.0.0.0 0.0.0.0 <default gateway address>
router ospf 1
default-information originate

Q: Interestingly, the ____________________ command tells the router to always advertise the default route, no matter whether the router’s default route is working or not.
A: default-information originate

Q: What is the OSPF three-step process?
A: 1. Create neighbor relationships
2. Build and flood LSAs
3. Each router independently computes its own IP routes and adds them to its routing table.

Q: Which "show" command lists which routing protocol is being used?
A: show ip protocols

Q: Would two routers having the same router-id configured stop them from forming an adjacency?
A: yes

Q: What is the default hello timer for OSPF?
A: 10

Q: What is the default dead timer for OSPF?
A: 40

Q: What is the default wait timer for OSPF?
A: 40

Q: What is the default retransmit timer for OSPF?
A: 5

Q: What is the default oob-resync timer for OSPF?
A: 40

Q: What does the "ip default-network" command do?
A: Configures a router with a gateway of last resort.

Q: What is the valid range for ospf process IDs?
A: 1-65535

Q: What does the following command do?:
default-information originate
A: Advertises the router's default route to all other routers, making their default route point toward the router that issued the command.  Often used to point to outside networks (the Internet).

Q: Why can't you route and internal hosts' private IP addresses on the internet?
A: Because Internet routers will drop packets with private IP addresses per RFC1918

Q: When configuring NAT inside and outside interfaces, do you have to configure all router sub-interfaces individually, or can you just configure the main interface?
A: You must configure them all individually.

Q: How do you calculate route cost?
A: 100/Bandwidth
For example, a T1 (1.544 Mbps) connection has a cost of 100/1.544 ~= 64.7 = Cost of 64

Q: What commands can be used to allow load balancing in ospf?
A: ip ospf cost,
bandwidth