What Blake just said below works best - I do this MED together with small-ers all the way to india for video conferencing customers sitting in silicon valley.
Thank You Bob Evans CTO > > > Stephen Satchell wrote on 9/24/2015 8:39 AM: >> 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. > > Jason, while others have offered acknowledgement of the behavior you are > seeing as well as solutions, I think it might be relevant to point out > that this is simply a matter of BGP best path selection. BGP does not > use AS path length (hops) as its primary path selector. Search for "bgp > best path selection" to find out more about how BGP selects the best > path. As others have noted, local pref is often utilized to control > routing and should be your preferred way to control path selection in > addition to AS path length. However, the ultimate way to control routing > would be to advertise more specific prefixes via the path that you want > traffic to flow. > > --Blake >