Re: Two queries on calculating AS external routes

[Paresh Khatri <[e-mail]>]

Thanks Acee,

Looking back at my second query, I realise that I wasn't quite clear on what I was getting at (my apologies).  It should be phrased as such:

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
 - originated by two different ASBRs and the ASBRs are in different non-backbone areas.
 - the intra-area distance to the ASBR is the same for both paths (but of course, through a
   different area in each case)
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 ?

Would 16.4 (3) apply in this case or is it only applicable when you have multiple paths to the *same* ASBR ?

Thanks again,
Paresh.

  


-----Original Message-----
From: Mailing List [mailto:[e-mail]]On Behalf Of Acee
Lindem
Sent: Tuesday, 28 June 2005 12:18 PM
To: [e-mail]
Subject: Re: Two queries on calculating AS external routes


Hi Paresh,
See inline.

Paresh Khatri wrote:

>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 ?
>  
>
Yes. Both paths should both be installed.

>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 ?
>  
>
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

>All responses appreciated.
>
>Cheers,
>Paresh Khatri 
>
>  
>





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