OSPF virtual link configuration example

As shown in Figure 30, configure a virtual link between Switch B and Switch C to connect Area 2 to the backbone area. After configuration, Switch B can learn routes to Area 2.

1. Configure IP addresses for interfaces. (Details not shown.)

2. Enable OSPF:

   # Configure Switch A.

   <SwitchA> system-view
   [SwitchA] ospf 1 router-id 1.1.1.1
   [SwitchA-ospf-1] area 0
   [SwitchA-ospf-1-area-0.0.0.0] network 10.1.1.0 0.0.0.255
   [SwitchA-ospf-1-area-0.0.0.0] quit
   [SwitchA-ospf-1] quit
   

   # Configure Switch B.

   <SwitchB> system-view
   [SwitchB] ospf 1 router-id 2.2.2.2
   [SwitchB-ospf-1] area 0
   [SwitchB-ospf-1-area-0.0.0.0] network 10.1.1.0 0.0.0.255
   [SwitchB-ospf-1-area-0.0.0.0] quit
   [SwitchB-ospf-1] area 1
   [SwitchB–ospf-1-area-0.0.0.1] network 10.2.1.0 0.0.0.255
   [SwitchB–ospf-1-area-0.0.0.1] quit
   [SwitchB-ospf-1] quit
   

   # Configure Switch C.

   <SwitchC> system-view
   [SwitchC] ospf 1 router-id 3.3.3.3
   [SwitchC-ospf-1] area 1
   [SwitchC-ospf-1-area-0.0.0.1] network 10.2.1.0 0.0.0.255
   [SwitchC-ospf-1-area-0.0.0.1] quit
   [SwitchC-ospf-1] area 2
   [SwitchC–ospf-1-area-0.0.0.2] network 10.3.1.0 0.0.0.255
   [SwitchC–ospf-1-area-0.0.0.2] quit
   [SwitchC-ospf-1] quit
   

   # Configure Switch D.

   <SwitchD> system-view
   [SwitchD] ospf 1 router-id 4.4.4.4
   [SwitchD-ospf-1] area 2
   [SwitchD-ospf-1-area-0.0.0.2] network 10.3.1.0 0.0.0.255
   [SwitchD-ospf-1-area-0.0.0.2] quit
   [SwitchD-ospf-1] quit
   

   # Display the OSPF routing table on Switch B.

   [SwitchB] display ospf routing
   
             OSPF Process 1 with Router ID 2.2.2.2
                      Routing Table
   
                   Topology base (MTID 0)
   
    Routing for network
    Destination        Cost     Type    NextHop         AdvRouter       Area
    10.2.1.0/24        2        Transit 10.2.1.1        3.3.3.3         0.0.0.1
    10.1.1.0/24        2        Transit 10.1.1.2        2.2.2.2         0.0.0.0
    Total nets: 2
    Intra area: 2  Inter area: 0  ASE: 0  NSSA: 0
   

   The output shows that Switch B does not have routes to Area 2 because Area 0 is not directly connected to Area 2.

3. Configure a virtual link:

   # Configure Switch B.

   [SwitchB] ospf
   [SwitchB-ospf-1] area 1
   [SwitchB-ospf-1-area-0.0.0.1] vlink-peer 3.3.3.3
   [SwitchB-ospf-1-area-0.0.0.1] quit
   [SwitchB-ospf-1] quit
   

   # Configure Switch C.

   [SwitchC] ospf 1
   [SwitchC-ospf-1] area 1
   [SwitchC-ospf-1-area-0.0.0.1] vlink-peer 2.2.2.2
   [SwitchC-ospf-1-area-0.0.0.1] quit
   [SwitchC-ospf-1] quit
   

   # Display the OSPF routing table on Switch B.

   [SwitchB] display ospf routing
   
             OSPF Process 1 with Router ID 2.2.2.2
                      Routing Table
   
                   Topology base (MTID 0)
   
    Routing for network
    Destination        Cost     Type    NextHop         AdvRouter       Area
    10.2.1.0/24        2        Transit 10.2.1.1        3.3.3.3         0.0.0.1
    10.3.1.0/24        5        Inter   10.2.1.2        3.3.3.3         0.0.0.0
    10.1.1.0/24        2        Transit 10.1.1.2        2.2.2.2         0.0.0.0
   
    Total nets: 3
    Intra area: 2  Inter area: 1  ASE: 0  NSSA: 0
   

   The output shows that Switch B has learned the route 10.3.1.0/24 to Area 2.