Service Providers behaviour for dual homed enterprises

Thu Sep 24 13:39:54 UTC 2015

On 09/23/2015 02:38 PM, 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?
>
> Thanks in advance
>

That's been my experience, and with other sets of providers, too.

My current company is dual-homed with AT&T and Charter Fiber.  Those 
customers on UVerse come in the AT&T link no matter what we do with BGP 
to convince the cloud to let packets come in the fatter pipe.