Lab 4.2.4.2 Force OSPF DR And BDR Selection

Objective:

Force the DR and BDR election process.

Scenario:

You have been called back by your ISP because "Router C" has been moved to a 56K link but continues to become the DR. This is causing a great slowdown in their WAN operations because each LSA must travel down this one 56K connection.

Warning: Boot order will have the greatest effect on the DR/DBR election process unless a priority of "0" is given to a router.

From the "Router A" console

  1. Enter show ip ospf neighbor

What is the priority of all the routers in Area 0 ?

  1. To configure the router priority for the DR/BDR election process issue the following commands:
  • router-a(config)#interface fastethernet 0/0
  • router-a(config-if)#ip ospf priority 5
  1. Write the running-configuration to memory

From the "Router B" console

  1. Predict which router will now be the DR for Area 0 and then enter show ip ospf interface

Examine which router is the DR for Area 0 and report your findings.

  1. Issue the following commands on "Router B":
  • router-b(config)#interface fastethernet 0/0
  • router-b(config-if)#ip ospf priority 10
  1. Write the running-configuration to memory, reboot all the routers in Area 0 and wait one minute.

From the "Router C" console

  1. Enter show ip ospf neighbor

Which routers are the DR and BDR for Area 0? Was there a change?

Report the priority of all the other routers in Area 0

  1. Enter debug ip ospf events and then turn off "Router A" only and wait one minute

Predict which router will become the BDR after Router A is dead

  1. Enter undebug all after the election process has stopped

Which router became the DR and which became the BDR. Why?

From the "Router C" console

  1. To stop a router from becoming a DR/BDR issue the following commands:
  • router-a(config)#interface fastethernet 0/0
  • router-a(config-if)#ip ospf priority 0
  1. Write the running-configuration to memory and reboot all the routers in Area 0

From the "Router A" console

  1. Enter show ip ospf neighbor and report the priority of all the routers in Area 0 ?

  1. Change the priority of all the routers to "0", write the running-configurations of all routers to memory, and reboot all the routers in Area 0.

Report your findings below: