nanog mailing list archives

Re: AS 701 local-pref answer.


From: Mike Leber <mleber () he net>
Date: Sun, 16 Dec 2001 18:46:53 -0800 (PST)



Thank you for pointing that out.  I was being dense and reading way too
much into the statements:

smentzer () mentzer org wrote:
All the responses I have gotten indicate that UUnet does indeed set
local-pref on both customers and peers to 100 (or leave default in this
case).  Thanks for all the responses...

Especially when the 701 communities were already provided by German
Martinez.  *DOH*

In other words, 701 transit customers that actually want to ensure their
downstream customer routes are announced by 701 had better set the
appropriate community so that local pref gets set above 100.  By default
this is not done.

Pardon me while I get some much needed rest.

Mike.

On Sun, 16 Dec 2001, David Barak wrote:

Mike Leber wrote:

If they set local pref for both peers and customers
to 100 how do they
ensure that the customer transit routes are
announced to peers?

The reason I ask this is because if a customer 
announces a customer of
theirs to you that a peer also has as a customer >you
will have equal
length routes for the same destination AS.  While
there are many ways to
deterministicly prefer customer routes, local pref
is the most common.

AS 701 always announces the best route, as their
routers know it.  Their average AS-path length is
under 2, so it doesn't seem to be a problem.  If a
customer of AS 701 wants to insure that his/her route
is advertised in all cases, s/he could send a
community which AS701 edge devices could use to
manipulate local-preference upward.  [this was covered
in a previous posting on this topic]  I leave it to
your imagination whether peers would be permitted to
do this.

-David Barak
I only speak for myself.
"Quis custodes ipsos custodiet?" - Juvenal

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