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Re: The same prefix originated within two different ASs

Alan Barrett <barrett@daisy.ee.und.ac.za> Wed, 12 July 1995 08:02 UTC

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Date: Wed, 12 Jul 1995 09:57:53 +0200 (GMT+0200)
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From: Alan Barrett <barrett@daisy.ee.und.ac.za>
To: Vadim Antonov <avg@sprint.net>
cc: bgp@ans.net, bgpd@merit.edu
Subject: Re: The same prefix originated within two different ASs
In-Reply-To: <199507111933.PAA10350@titan.sprintlink.net>
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> >Can someone please reiterate to me, from experience, reasons why a prefix
> >shouldn't be advertised as originating from two separate ASs?
> 
> Because it breaks underlying assumption after AS-path based policies that
> all prefixes are split into groups by originating AS-es.

But an AS is a set of routers, not a set of prefixes.

> I.e. if you
> do that somebody's preferences or filters based on originating AS-es
> may behave incoherently, potentially creating persistent routing loops.

Can you give an example?  I don't immediately see a way for persistent
routing loops to arise from a prefix being originated by several ASes.  

--apb (Alan Barrett)

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