Objective
Configure Multi-Area OSPF based on the topology. R1 is in Area 1, R2 and R3 are ABRs connecting to the Backbone (Area 0), and R4 is in Area 2.
Lab Topology
| Router | Interface | IP Address | OSPF Area |
|---|---|---|---|
| R1 | Gi0/0 |
192.168.12.1/30 |
Area 1 |
| R1 | Loopback 1 |
10.10.10.1/24 |
Area 1 |
| R2 | Gi0/0 (to R1) |
192.168.12.2/30 |
Area 1 |
| R2 | Gi0/1 (to R3) |
192.168.23.1/30 |
Area 0 |
| R2 | Loopback 1 |
10.10.20.1/24 |
Area 0 |
| R3 | Gi0/0 (to R2) |
192.168.23.2/30 |
Area 0 |
| R3 | Gi0/1 (to R4) |
192.168.34.1/30 |
Area 2 |
| R3 | Loopback 1 |
10.10.30.1/24 |
Area 0 |
| R4 | Gi0/0 |
192.168.34.2/30 |
Area 2 |
| R4 | Loopback 1 |
10.10.40.1/24 |
Area 2 |
Task 1 - Configure R1 (Internal Area 1)
R1(config)# hostname R1 R1(config)# interface Loopback 1 R1(config-if)# ip address 10.10.10.1 255.255.255.0 R1(config-if)# exit R1(config)# interface GigabitEthernet0/0 R1(config-if)# ip address 192.168.12.1 255.255.255.252 R1(config-if)# no shutdown R1(config)# router ospf 10 R1(config-router)# router-id 1.1.1.1 R1(config-router)# network 10.10.10.0 0.0.0.255 area 1 R1(config-router)# network 192.168.12.0 0.0.0.3 area 1
Task 2 - Configure R2 (ABR: Area 1 & 0)
R2(config)# hostname R2 R2(config)# interface Loopback 1 R2(config-if)# ip address 10.10.20.1 255.255.255.0 R2(config-if)# exit R2(config)# interface Gi0/0 ! Link to R1 R2(config-if)# ip address 192.168.12.2 255.255.255.252 R2(config-if)# no shutdown R2(config)# interface Gi0/1 ! Link to R3 R2(config-if)# ip address 192.168.23.1 255.255.255.252 R2(config-if)# no shutdown R2(config)# router ospf 10 R2(config-router)# router-id 2.2.2.2 R2(config-router)# network 10.10.20.0 0.0.0.255 area 0 R2(config-router)# network 192.168.12.0 0.0.0.3 area 1 R2(config-router)# network 192.168.23.0 0.0.0.3 area 0
Task 3 - Configure R3 (ABR: Area 0 & 2)
R3(config)# hostname R3 R3(config)# interface Loopback 1 R3(config-if)# ip address 10.10.30.1 255.255.255.0 R3(config-if)# exit R3(config)# interface Gi0/0 ! Link to R2 R3(config-if)# ip address 192.168.23.2 255.255.255.252 R3(config-if)# no shutdown R3(config)# interface Gi0/1 ! Link to R4 R3(config-if)# ip address 192.168.34.1 255.255.255.252 R3(config-if)# no shutdown R3(config)# router ospf 10 R3(config-router)# router-id 3.3.3.3 R3(config-router)# network 10.10.30.0 0.0.0.255 area 0 R3(config-router)# network 192.168.23.0 0.0.0.3 area 0 R3(config-router)# network 192.168.34.0 0.0.0.3 area 2
Task 4 - Configure R4 (Internal Area 2)
R4(config)# hostname R4 R4(config)# interface Loopback 1 R4(config-if)# ip address 10.10.40.1 255.255.255.0 R4(config-if)# exit R4(config)# interface Gi0/0 ! Link to R3 R4(config-if)# ip address 192.168.34.2 255.255.255.252 R4(config-if)# no shutdown R4(config)# router ospf 10 R4(config-router)# router-id 4.4.4.4 R4(config-router)# network 10.10.40.0 0.0.0.255 area 2 R4(config-router)# network 192.168.34.0 0.0.0.3 area 2
Task 5 - Verification
Ensure adjacencies are formed and inter-area routes are present in the routing table.
R1# show ip ospf neighbor R1# show ip route ospf O IA 192.168.23.0 [110/2] via 192.168.12.2, GigabitEthernet0/0 O IA 192.168.34.0 [110/3] via 192.168.12.2, GigabitEthernet0/0 R1# show ip ospf interface brief