Technical data

BLADE OS 5.1 Application Guide
BMD00136, November 2009 Chapter 11: OSPF
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Virtual Links
Usually, all areas in an OSPF AS are physically connected to the backbone. In some cases where
this is not possible, you can use a virtual link. Virtual links are created to connect one area to the
backbone through another non-backbone area (see Figure 22 on page 146).
The area which contains a virtual link must be a transit area and have full routing information.
Virtual links cannot be configured inside a stub area or NSSA. The area type must be defined as
transit using the following command:
The virtual link must be configured on the routing devices at each endpoint of the virtual link, though
they may traverse multiple routing devices. To configure a G8000 as one endpoint of a virtual link,
use the following command:
where <link number> is a value between 1 and 3, <area index> is the OSPF area index of the
transit area, and <router ID> is the IP address of the virtual neighbor, the routing device at the
target endpoint. Another router ID is needed when configuring a virtual link in the other direction.
To provide the G8000 with a router ID, see the following section Router ID.
For a detailed configuration example on Virtual Links, see “Example 2: Virtual Links” on page 163.
>> (config-router-ospf)# area <area index> type transit
>> (config-router-ospf)# area-virtual-link <link number> neighbor-router <router ID>