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Re: bgp update destroying transit on redback routers ?
From: Alexandre Snarskii <snar () snar spb ru>
Date: Fri, 2 Dec 2011 18:35:54 +0400

On Thu, Dec 01, 2011 at 04:56:43PM -0500, Jeff Tantsura wrote:

Let me take it over from now on, I'm the IP Routing/MPLS Product Manager 
at Ericsson responsible for all routing protocols.
There's nothing wrong in checking ASN in AGGREGATOR, we don't really want 
see ASN 0 anywhere, that's how draft-wkumari-idr-as0 (draft-ietf-idr-as0-00) 
came into the worlds.

This draft says that

If a BGP speaker receives a route which has an AS number of zero in the
AS_PATH (or AS4_PATH) attribute, it SHOULD be logged and treated as a 
WITHDRAW. This same behavior applies to routes containing zero as the 
Aggregator or AS4 Aggregator.

but observed behaviour was more like following: 

If a BGP speaker receives [bad route] it MUST close session immediately 
with NOTIFICATION Error Code 'Update Message Error' and subcode 'Error with 
optional attribute'.

In theory, there is no difference between theory and practice. 
But, in practice, there is. 

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