Objective
Configure Multi-Area OSPF. R1 in Area 1, R2 and R3 in Area 0 (Backbone), and R4 in Area 2.
Lab Topology
R1 (Area 1) <---> R2 (ABR) <---> R3 (ABR) <---> R4 (Area 2)
R1-R2 Link: Area 1 | R2-R3 Link: Area 0 | R3-R4 Link: Area 2
Task 1 – Configure R1 (Area 1)
R1(config)# router ospf 1 R1(config-router)# router-id 1.1.1.1 R1(config-router)# network 10.1.2.0 0.0.0.255 area 1
Task 2 – Configure R2 (ABR: Area 1 & 0)
R2(config)# router ospf 1 R2(config-router)# router-id 2.2.2.2 R2(config-router)# network 10.1.2.0 0.0.0.255 area 1 ! Towards R1 R2(config-router)# network 10.2.3.0 0.0.0.255 area 0 ! Towards R3
Task 3 – Configure R3 (ABR: Area 0 & 2)
R3(config)# router ospf 1 R3(config-router)# router-id 3.3.3.3 R3(config-router)# network 10.2.3.0 0.0.0.255 area 0 ! Towards R2 R3(config-router)# network 10.3.4.0 0.0.0.255 area 2 ! Towards R4
Task 4 – Configure R4 (Area 2)
R4(config)# router ospf 1 R4(config-router)# router-id 4.4.4.4 R4(config-router)# network 10.3.4.0 0.0.0.255 area 2
Task 5 – Verification
Check routing table on R1. It should see routes from other areas as O IA (OSPF Inter-Area).
R1# show ip route ospf O IA 10.2.3.0 [110/2] via 10.1.2.2, GigabitEthernet0/0 O IA 10.3.4.0 [110/3] via 10.1.2.2, GigabitEthernet0/0