Subject: Originating Summary LSAs

From: Igor Miroshnik <[email-masked]>
Date: Wed, 18 Dec 2002 14:18:28 -0500

Hi,

Should an ASBR be advertised into an area which has its own intra-area
route to that ASBR? Does the answer differ if the router supports only
RFC1583? For my understanding of RFC1583, RFC2178, and RFC2328, it should
be advertised. Am I mistaking?

Thanks,
Igor

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From: Acee Lindem <[email-masked]>
Date: Fri, 20 Dec 2002 12:00:20 -0500

> be advertised. Am I mistaking?

Igor,

My interpretation of section 12.4.3 is that an OSPF router should
generate a summary into areas other than the area containing the best
path (even if an intra-area path exists to the router in other areas).

        o   Else, if the destination of this route is an AS boundary
            router, a summary-LSA should be originated if and only
            if the routing table entry describes the preferred path
            to the AS boundary router (see Step 3 of Section 16.4).
            If so, a Type 4 summary-LSA is originated for the
            destination, with Link State ID equal to the AS boundary
            router's Router ID and metric equal to the routing table
            entry's cost. Note: these LSAs should not be generated
            if Area A has been configured as a stub area.

The determination of the best path to an ASBR changed from RFC 1583 to
RFC 2178.

I'd be interested if there are implementations that suppress the
type 4 summary for areas having any intra-area path.

Thanks,
Acee

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Acee