[147584] in North American Network Operators' Group
RE: local_preference for transit traffic?
daemon@ATHENA.MIT.EDU (Holmes,David A)
Thu Dec 15 01:32:29 2011
From: "Holmes,David A" <dholmes@mwdh2o.com>
To: Keegan Holley <keegan.holley@sungard.com>, NANOG <nanog@nanog.org>
Date: Wed, 14 Dec 2011 22:31:29 -0800
In-Reply-To: <CABO8Q6ThEL_rHYxoJ2bg8fKsfa3uPKS-EVBgu1EPu9ic73_rrA@mail.gmail.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
For this very reason I have advocated using longest prefix BGP routing for =
some years now, and checking periodically for the expected path, as it beca=
me obvious from investigating traceroutes that traffic was not being routed=
as intended using AS prepends.
-----Original Message-----
From: Keegan Holley [mailto:keegan.holley@sungard.com]
Sent: Wednesday, December 14, 2011 10:08 PM
To: NANOG
Subject: local_preference for transit traffic?
Had in interesting conversation with a transit AS on behalf of a customer
where I found out they are using communities to raise the local preference
of routes that do not originate locally by default before sending to a
other larger transit AS's. Obviously this isn't something that was asked
of them and it took a few days to find since the customer is not a large
company and neither them nor my company has a link or business relationship
with the AS in question. This seemed strange to me for obvious reasons,
but I was curious if anyone else was doing this and why. You obviously
cannot use prepend to affect transit traffic again for obvious reasons.
MED is a weak metric but it at least only affects traffic that was already
going to transit your AS. The larger transit AS was favoring a lower
bandwidth link for the customer and causing them to drop packets
mysteriously. Just wondering if this practice seemed as strange to others
as it does to me.
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