Lab 25 - OSPF Virtual Link Example 2

Prerequisites: CCNP level skills.

Topology

Pic. 1 - OSPF Topology.

Icons designed by: Andrzej Szoblik - http://www.newo.pl

Task 1

Configure OSPF in area 0, and area 1 as per pic. 1.

Task 2
Configure OSPF in area 2. Ensure full reachability in OSPF domain.

Task 3
Configure OSPF in area 3. Ensure full reachability in OSPF domain.

Lab Solution

Task 1

Configure OSPF in area 0, and area 1 as per pic. 1.

R1 Configuration:

!

router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 network 10.1.12.1 0.0.0.0 area 1
 network 10.1.13.1 0.0.0.0 area 0
 network 172.16.101.1 0.0.0.0 area 1

!

R2 Configuration:

!

router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 network 10.1.12.2 0.0.0.0 area 1
 network 172.16.102.2 0.0.0.0 area 1

!

R3 Configuration:

!

router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 network 10.1.13.3 0.0.0.0 area 0
 network 10.1.35.3 0.0.0.0 area 0
 network 172.16.103.3 0.0.0.0 area 0

!

R5 Configuration:

!

router ospf 1
 router-id 5.5.5.5
 log-adjacency-changes
 network 10.1.35.5 0.0.0.0 area 0
 network 172.16.105.5 0.0.0.0 area 0

!

Task 2

Configure OSPF in area 2. Ensure full reachability in OSPF domain.

R1 Configuration:

!

router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 area 1 virtual-link 2.2.2.2
 network 10.1.12.1 0.0.0.0 area 1
 network 10.1.13.1 0.0.0.0 area 0
 network 172.16.101.1 0.0.0.0 area 1
!

R2 Configuration:

!

router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 area 1 virtual-link 1.1.1.1
 network 10.1.12.2 0.0.0.0 area 1
 network 10.1.24.2 0.0.0.0 area 2
 network 172.16.102.2 0.0.0.0 area 1

!

R4 Configuration:

!

router ospf 1
 router-id 4.4.4.4
 log-adjacency-changes
 network 10.1.24.4 0.0.0.0 area 2

!

Verification:

Pic. 2 - R2's Neighbor Adjacency.

Note!
All areas must be connected to the backbone area (area 0) through ABR. In this topology area 1 does not have physical connection to area 0. Virtual link between R1 and R2 is the extension of area 0 and R2 becomes ABR allowing area 2 to receive all the prefixes.

Pic. 3 - R4's Routing Table.

Task 3

Configure OSPF in area 3. Ensure full reachability in OSPF domain.

Note!
Area 3 has similar issue as area 2 in task 2. It needs physical connection to the backbone area which it lacks. Since R2 is already an ABR through virtual link between R1 and R2, another virtual link is required between R2 and R4 in order for R4 to be connected to the backbone area (area 0). This should allow R6 to receive all prefixes.

R2 Configuration:

!

router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 area 1 virtual-link 1.1.1.1
 area 2 virtual-link 4.4.4.4
 network 10.1.12.2 0.0.0.0 area 1
 network 10.1.24.2 0.0.0.0 area 2
 network 172.16.102.2 0.0.0.0 area 1
!

R4 Configuration:

!

router ospf 1
 router-id 4.4.4.4
 log-adjacency-changes
 area 2 virtual-link 2.2.2.2
 network 10.1.24.4 0.0.0.0 area 2
 network 10.1.46.4 0.0.0.0 area 3
!

R6 Configuration:

!

router ospf 1
 router-id 6.6.6.6
 log-adjacency-changes
 network 10.1.46.6 0.0.0.0 area 3
 network 172.16.106.6 0.0.0.0 area 3
!

Verification:

Pic. 4 - R4's Neighbor Adjacency.

Pic. 5 - R6's Routing Table.