Foundry Networks Switch and Router Installation And Configuration Manual page 586

Foundry Switch and Router Installation and Configuration Guide
The Foundry implementation of NSSA is based on RFC 1587.
Figure 17.5 shows an example of an OSPF network containing an NSSA.
Figure 17.5 OSPF network containing an NSSA
This example shows two routing domains, a RIP domain and an OSPF domain. The ASBR inside the NSSA
imports external routes from RIP into the NSSA as Type-7 LSAs, which the ASBR floods throughout the NSSA.
The ABR translates the Type-7 LSAs into Type-5 LSAs. If an area range is configured for the NSSA, the ABR also
summarizes the LSAs into an aggregate LSA before flooding the Type-5 LSA(s) into the backbone.
Since the NSSA is partially "stubby" the ABR does not flood external LSAs from the backbone into the NSSA. To
provide access to the rest of the Autonomous System (AS), the ABR generates a default Type-7 LSA into the
NSSA.
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RIP Domain
BigIron
BigIron
Internal ASBR
NSSA Area 1.1.1.1
OSPF Area 0
Backbone
BigIron
OSPF ABR
December 2000