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From: Pat Murphy - (650)329-4044 (pmurphy_at_NOC.USGS.NET)
Date: Fri Sep 13 2002 - 12:35:39 CDT
>So my question is, does NSSA ABR(R4) must inject type7 default
>route in to AREA2 or we need manually configure default route
>on R4 for the RIP I destination network.
A default route is not necessary on R4 for it to reach the RIP-I
destinations since R4 can compute their next hops from their Type 5
LSAs. However if R4 originates a default Type 7 LSA into NSSA 2 that R5
prefers, then R5 could reach the RIP-I destinations through R4 via its
By default, all of an NSSA ABRs, such as R4, are expected to originate a
type 7 LSA for default when none of the NSSA's internal routers, such as
R5, orignate a Type 7 LSA for default, even when they don't possess an
installed default path. I am not sure about RFC 1587, but this
requirement is explicitly described in the lastest NSSA draft.
Compliments of a suggestion of Alex Zinin's, I posted a draft titled
Type 5 to Type 7 Translation
which is still available. It would allow the partial import of Type 5
LSAs, such as your RIP I routes, with aggregation. You can also find it
Quite frankly it seems logical that an NSSA should be able to import a
subset of an OSPF domain's Type 5 external LSAs complete with
aggregation, given that it can import external routes to networks
outside the AS via its external links. While I hope to repost this draft
soon, its current content is fairly clean.