[163525] in North American Network Operators' Group
Re: Single AS multiple Dirverse Providers
daemon@ATHENA.MIT.EDU (Leo Bicknell)
Mon Jun 10 14:43:12 2013
From: Leo Bicknell <bicknell@ufp.org>
In-Reply-To: <FF9419BD-E7DB-4C51-B6F4-1F8B2691CFCC@ianai.net>
Date: Mon, 10 Jun 2013 13:42:12 -0500
To: "Patrick W. Gilmore" <patrick@ianai.net>
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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On Jun 10, 2013, at 12:08 PM, Patrick W. Gilmore <patrick@ianai.net> =
wrote:
>> however, providers a/b at site1 do not send us the two /24s from
>> site b..
>=20
> This is probably incorrect.
>=20
> The providers are almost certainly sending you the prefixes, but your =
router is dropping them due to loop detection. To answer your later =
question, this is the definition of 'standard' as it is written into the =
RFC.
>=20
> Use the allow-as-in style command posted later in this thread to fix =
your router.
I've done this many places, and find allow-as-in can be, uh, =
problematic. :) Everyone says to just turn it on, but it's possible to =
get some strange paths in your table that way, in some circumstances.
For most users having a default route is just as good of a solution. =
Each site will have a full table minus the small number of prefixes at =
the other site, and a static default will get packets to your upstream =
that has those routes. Don't like a default? Just static the netblocks =
at the other side to a particular provider. Already have a default =
because you weren't taking full tables? You're good to go, no special =
config needed.
Of course it depends on what your site-to-site requirements are, if they =
are independent islands or talking to each other with critical data all =
the time.
--=20
Leo Bicknell - bicknell@ufp.org - CCIE 3440
PGP keys at http://www.ufp.org/~bicknell/
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