Subject: Two queries on calculating AS external routes

From: Paresh Khatri <[email-masked]>
Date: Mon, 27 Jun 2005 20:53:38 -0400

Hi all,

I've got a couple of queries on Section 16.4 of RFC2328 that I hope someone
can help me with.

1)
When determining that preferred routing table entry for the ASBR in step
(4), what happens if we end up with two equal-cost intra-area routes (for
the same area) to the ASBR (this is after all the pruning from 16.4.1 etc) ?
 Will both routes be installed in the routing table ?

2)

Looking at step (6) now.  If we have two, and only two, paths to a
destination N, with the following characteristics: 
 - same route-type (say, Type 2 external) 
 - same type-2 metric
 - both are intra-area routes but for different non-backbone areas ( so we
still end up with 2 paths after 16.4.1)
 - the intra-area distance to the ASBR is the same for both paths
Will both paths be installed in the routing table ?  If so, would that not
contradict section 16.8, which states that all equal-cost paths for a route
should be associated with the same area ?

All responses appreciated.

Cheers,
Paresh Khatri

---

From: Acee Lindem <[email-masked]>
Date: Mon, 27 Jun 2005 22:18:27 -0400

Hi Paresh,
See inline.

> Will both routes be installed in the routing table ?
Yes. Both paths should both be installed.

>should be associated with the same area ?
For equal cost paths to an ASBR, the path through the area with the 
highest ID should be
chosen (refer to 16.4 (3)).

Hope this helps,
Acee