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Not-So-Stubby Area Configuration
To expand upon the idea of advertising summarized routes, the area area-
id range network_address network_mask
command is used to summarize
intra-area routes on an ABR. Similarly, we can summarize external routes on
an autonomous system boundary router (ASBR) with the command summary-
address network_address network_mask
. Proper use of these summarization
tools can greatly reduce the number of routes that have to be maintained by
a router, thus reducing memory and processor overhead.
RouterC will be an even more complex configuration. Not only is
RouterC part of an NSSA, it also participates in a RIP routing process. In
order to exchange its OSPF and RIP routes, RouterC must perform route
redistribution (route redistribution is the focus of Chapter 10):
RouterC(config)#router ospf 24
RouterC(config-router)#redistribute rip
where rip is the routing protocol whose routes are being injected into the
OSPF routing process.
RouterC(config-router)#network area 1
RouterC(config-router)#default-metric 128
where 128 is the OSPF metric value to be assigned to routes being redistrib-
uted into the OSPF routing process.
RouterC(config-router)#area 1 nssa
RouterC(config-router)#router rip
This enables the RIP routing process on the router.
RouterC(config-router)#redistribute ospf 24
where ospf 24 is the routing process whose routes are being injected into the
RIP routing process.
RouterC(config-router)#default-metric 3
where 3 is the RIP metric value (hop count) to be assigned to routes being
redistributed into the RIP routing process.
RouterD is internal to the RIP routing process. Therefore, RouterD does
not require any NSSA-specific configuration:
RouterD(config)#router rip
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