[184011] in North American Network Operators' Group
Re: Service Providers behaviour for dual homed enterprises
daemon@ATHENA.MIT.EDU (Mark Tinka)
Thu Sep 24 03:52:02 2015
X-Original-To: nanog@nanog.org
To: Jason Bullen <jmbullen21@gmail.com>, nanog@nanog.org
From: Mark Tinka <mark.tinka@seacom.mu>
Date: Thu, 24 Sep 2015 09:51:55 +0200
In-Reply-To: <CALZ5zxgNp5FOJAen-3pKT0m6r1Oz=Ep6-BtK9GjOqUL0b6BQ+Q@mail.gmail.com>
Errors-To: nanog-bounces@nanog.org
On 23/Sep/15 23:38, Jason Bullen wrote:
> I've always worked in enterprise only so I thought you guys might be able
> to help me with this one.
> We are dual homed to Verizon and AT&T. We prepend all our prefixes out
> AT&T to make them least preferred. During a recent issue we found some
> users were coming in via AT&T. Using various looking glasses it looks like
> if I use an AT&T server(route-server.ip.att.net) the best path is the
> prepended route through AT&T; in fact,I don't even see the VZB route. If I
> use a 3rd party looking glass(router-server.he.net) I see what I
> anticipated, which is the shorter AS-Path through VZB.
>
> So if my research is correct, the internet prefers Verizon UNLESS they are
> a direct AT&T customer then they would use the AT&T circuit.
> Is this a standard practice that I should assume to encounter?
ISP's will generally set a higher LOCAL_PREF toward their customers than
to any other destination out of their network.
It's the money shot.
Mark.
