Re: [sidr] [Idr] AS_SET depreciation (RFC6472) and BGP multipath

Jeffrey Haas <jhaas@pfrc.org> Wed, 28 March 2012 20:55 UTC

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Date: Wed, 28 Mar 2012 16:55:22 -0400
From: Jeffrey Haas <jhaas@pfrc.org>
To: Christopher Morrow <morrowc.lists@gmail.com>
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References: <alpine.LFD.2.02.1203281401410.2692@jamaica.dcs.gla.ac.uk> <7309FCBCAE981B43ABBE69B31C8D21391B3EBFD895@EUSAACMS0701.eamcs.ericsson.se> <FBFDBAE5-9BF8-4708-9240-B775CAF46D56@raszuk.net> <7309FCBCAE981B43ABBE69B31C8D21391B3EBFD924@EUSAACMS0701.eamcs.ericsson.se> <alpine.LFD.2.02.1203281618090.2692@jamaica.dcs.gla.ac.uk> <CAL9jLaYqMwXVNKsHuBf_r8h==CGoee+D9k89Q4AZqT49jOQK1A@mail.gmail.com> <4F733C79.8080600@raszuk.net> <CAL9jLabVcWMtpu8usUS5w_BVPCG8ihvDcVjWbhnj_u6H-cdZkw@mail.gmail.com> <4F733FBE.1020902@raszuk.net> <CAL9jLaZJEkiJi3DPLTY35Ag9ynhTejjv09yx6NH4Oohwe975hg@mail.gmail.com>
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Cc: "idr@ietf.org List" <idr@ietf.org>, Paul Jakma <paul@jakma.org>, sidr wg list <sidr@ietf.org>
Subject: Re: [sidr] [Idr] AS_SET depreciation (RFC6472) and BGP multipath
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Chris,

On Wed, Mar 28, 2012 at 12:45:22PM -0400, Christopher Morrow wrote:
> ah yes, was thinking of local-as. the 'replace-as' seems like
> loop-creation, joy.

It can.  The use of replace-as is typically in situations where you need to
replace private AS numbers with a public number. This is typically done when
you have deployments that have a mix of private and public ASes behind a
common transit carrier and "remove-private" isn't sufficient.

The required behavior in order to avoid problems here is to make sure that
the set of ASes involved are behind that common carrier and either are not
multi-homed to the wider Internet (unlikely since they have private ASes) or
are applying appropriate AS filtering to manually suppress loops.

-- Jeff