mailing list archives
RE: bgp update destroying transit on redback routers ?
From: Jeff Tantsura <jeff.tantsura () ericsson com>
Date: Fri, 2 Dec 2011 17:14:35 -0500
You are right, the behavior is exactly as per RFC4271 section 6:
"When any of the conditions described here are detected, a
NOTIFICATION message, with the indicated Error Code, Error Subcode, and Data fields, is sent, and the BGP connection is
So because ASN 0 in AGGREGATOR is seen as a malformed UPDATE we send 3/9 and close the connection.
Ideally it should be treated as "treat-as-withdraw" as per draft-chen-ebgp-error-handling, however please note - this
is still a draft,
not a normative document and with all my support it takes time to implement.
Once again, we understand the implications for our customers and hence going to disable ASN 0 check.
P.S. We have strong evidence that the update in question was caused by a bug on a freshly updated router (I'm not going
to disclose the vendor)
From: Alexandre Snarskii [mailto:snar () snar spb ru]
Sent: Friday, December 02, 2011 6:36 AM
To: Jeff Tantsura
Cc: nanog () nanog org
Subject: Re: bgp update destroying transit on redback routers ?
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
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.
- Re: bgp update destroying transit on redback routers ?, (continued)