Understanding the network.pdf - Back to Home

to asbr-a1 was a remote office that was connected to the larger internetwork, we
could reconfigure area 192.168.0.96 on asbr-a1 as an NSSA area and have the
routing information redistributed into the OSPF process. The OSPF routing
subcommand is used to designate an area as an NSSA:
asbr-a1(config-router)#area 192.168.0.96 nssa
The configuration on ir-a2 looks like this:
rip 89
network 192.168.64.0
network 192.168.65.0
network 192.168.66.0
network 192.168.67.0
router ospf 34
network 192.168.0.98 0.0.0.0 area 192.168.0.96
area 192.168.0.96 nssa
redistribute rip subnets
All the routes redistributed from the NSSA network will appear as NSSA type 2
routes (N2). When configuring an area as an NSSA, all the routers in the area must
be configured to recognize the area as an NSSA.
Adjusting OSPF's Behavior
It is not always possible to construct a network topology that allows for proper
router/area segmentation. It is possible to connect an ABR across a non-area-zero
transit area. A virtual link is established between a true ABR and the "virtual ABR"
via the OSPF subprocess configuration command . Each side of the link uses the router id of the remote
end. Let's examine a virtual link configuration between ir-a1 and asbr-a2 (the
command will display the router's OSPF ID):
hostname ir-a1
!
router ospf 78