© Copyright IBM Corp. 2011 Chapter 22. OSPF 273
Example 2: Virtual Links
In the example shown in Figure 31, area 2 is not physically connected to the
backbone as is usually required. Instead, area 2 will be connected to the backbone
via a virtual link through area 1. The virtual link must be configured at each endpoint.
Figure 31. Configuring a Virtual Link
Note: OSPFv2 supports IPv4 only. IPv6 is supported in OSPFv3 (see “OSPFv3
Implementation in IBM N/OS” on page 279).
Configuring OSPF for a Virtual Link on Switch #1
1. Configure IP interfaces on each network that will be attached to the switch.
In this example, two IP interfaces are needed:
– Interface 1 for the backbone network on 10.10.7.0/24
– Interface 2 for the transit area network on 10.10.12.0/24
2. Configure the router ID.
A router ID is required when configuring virtual links. Later, when configuring the
other end of the virtual link on Switch 2, the router ID specified here will be used
as the target virtual neighbor (
nbr
) address.
3. Enable OSPF.
4. Define the backbone.
RS G8000(config)# interface ip 1
RS G8000(config-ip-if)# ip address 10.10.7.1
RS G8000(config-ip-if)# ip netmask 255.255.255.0
RS G8000(config-ip-if)# enable
RS G8000(config-ip-if)# exit
RS G8000(config)# interface ip 2
RS G8000(config-ip-if)# ip address 10.10.12.1
RS G8000(config-ip-if)# ip netmask 255.255.255.0
RS G8000(config-ip-if)# enable
RS G8000(config-ip-if)# exit
RS G8000(config)
#
ip router-id 10.10.10.1
RS G8000(config)# router ospf
RS G8000(config-router-ospf)# enable
RS G8000(config-router-ospf)# area 0 area-id 0.0.0.0
RS G8000(config-router-ospf)# area 0 type transit
RS G8000(config-router-ospf)# area 0 enable
Switch 2
Switch 2 Switch 1
Switch 1
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