Virtual Links - Lenovo Flex System Fabric CN4093 Application Manual

Virtual Links

432
CN4093 Application Guide for N/OS 8.2
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 46 on page 423).
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:
CN4093(config­router­ospf)# area <area index> type transit
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
CN4093 as one endpoint of a virtual link, use the following command:
CN4093(config­router­ospf)# area­virtual­link <link number> neighbor­router
<router ID>
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 (nbr),
the routing device at the target endpoint. Another router ID is needed when
configuring a virtual link in the other direction. To provide the CN4093 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 438.