Lab 4.3.2.1 Force OSPF Router ID

Objective:

Stabilize OSPF router ID with a loopback interface.

Scenario:

Every time there is power outage in the network, the router IDs change over to the Serial interface IP address. This is causing a great deal of instability because every time the router ID changes all the routers in OSPF Area 0 run the SPF algorithm.

(NOTE: Do not erase routers from the previous lab)

From the "Router C" console

  1. Issue the following commands:
  • router-c(config)#interface fastethernet 0/0
  • router-c(config-if)#no ip address 206.202.16.254 255.255.255.0
  • router-c(config-if)#control Z

  1. Are there any error messages? Why?

  1. Write the running-configuration to memory and reboot "Router C"
  2. After the router boots enter enable exec mode and issue the command show running-config
  1. Is OSPF still configured properly?

  1. Issue the following commands:
  • router-c(config)#interface loopback 0
  • router-c(config-if)#ip address 1.1.16.254 255.255.255.0
  • router-c(config-if)#interface fastethernet 0/0
  • router-c(config-if)#ip address 206.202.16.254 255.255.255.0
  • router-c(config-if)#no shutdown
  • router-c(config-if)#router ospf 1
  • router-c(config-router)#network 206.202.16.0 0.0.0.255 area 0
  • router-c(config-router)#control Z
  1. Write the running-configuration to memory and enter the command show ip interface

What is the purpose of a loopback address?

  1. Place a loopback interface on "Router A" and then enter show ip ospf neighbor

What is the router id of "Router C"

  1. Add loopback addresses to all the routers in OSPF area 0, write the running- configurations of all the routers to memory, and then reboot all the routers in Area 0

From the "Router A" console

  1. Enter enable exec mode and issue the command show ip ospf neighbor

What are the router IDs of all the routers in OSPF area 0?