Subject: forwarding address

From: query OSPF <[email-masked]>
Date: Wed, 4 Feb 2004 13:19:25 -0000

I have one doubt
regarding AS external routes. In section 16.4, step (3), it says that "If
the forwarding address is non-zero, look up the forwarding address in the
routing table. The matching routing table entry must specify an intra-area
or inter-area path; if no such path exists, do nothing with the LSA and
consider the next in the list". And in section 12.4.4.1, it says that "Note
that when the forwarding address field is non-zero, it should point to a
router belonging to another Autonomous System". My question is: if the
forwarding address points to a router in another AS, how can you get an
intra-area or inter-area route to it?

regards

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From: Acee Lindem <[email-masked]>
Date: Wed, 4 Feb 2004 09:15:02 -0500

First of all, please refrain from using rich text messages
on the list. They are more difficult to handle.

----- Original Message -----
From: query OSPF
To: [email-masked]
Sent: Wednesday, February 04, 2004 8:19 AM
Subject: forwarding address

> intra-area or inter-area route to it?

If the ASBR's next-hop router has an interface on a multi-access network
that is part of the OSPF routing domain. Refer to the discussion of "forwarding
address" in section 2.3 or RFC 2328.

Thanks,
Acee

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From: Mike Fox <[email-masked]>
Date: Wed, 4 Feb 2004 09:48:00 -0500

> address" in section 2.3 or RFC 2328.

I've asked this same question on this list and got this same answer.  I
still don't like it though, because I thought the point of the forwarding
address was to advertise a default route on behalf of a router who can't
advertise it himself.  If the default router has an interface that's part
of the OSPF domain, then he can advertise himself as default router and no
forwarding address is needed, IMO.   However the response to my objection
is that if the forwarding address is an external address, there's no
guarantee that other OSPF routers can reach it.  Kind of a catch-22: the
only time it's really needed is the time you can't be sure it can be
reached.

Mike
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