Cisco CCNP and CCIE Study Notes

Consider the network of four routers above running OSPF. Here is the sample output from router R1 showing the neighbor relationships -

R1#sh ip ospf neighbor

Neighbor ID   Pri State        Dead Time  Address       Interface
2.2.2.2         1 2WAY/DROTHER 00:00:35   192.168.1.2   Ethernet0
3.3.3.3         1 FULL/BDR     00:00:37   192.168.1.3   Ethernet0
4.4.4.4         1 FULL/DR      00:00:39   192.168.1.4   Ethernet0

Now consider the network changed as indicated in the diagram above. The four routers have been split into pairs that are in separate OSPF domains. Consequently, R1 has only R3 as a neighbor and vice-versa and the same is the case with R2 and R4. Note, in particular, that the four routers are still on the same subnet and with the same interface addresses as before.

Router R1

R1#sh ip ospf neighbor

Neighbor ID   Pri State        Dead Time   Address       Interface
3.3.3.3         1 FULL/BDR     00:00:39    192.168.1.3   Ethernet0

Router R2

R2#sh ip ospf neighbor

Neighbor ID   Pri State        Dead Time  Address       Interface
4.4.4.4       1   FULL/DR      00:00:33    192.168.1.4  Ethernet0

Your task in this problem is add the necessary configuration to the four routers to achieve what is shown in the second figure.