[c-nsp] bgp transit, selecting providers based on source IP

[Peter Rathlev]

On Tue, 2008-03-25 at 18:11 +0000, Wayne Lee wrote:
> We currently have 3 transit providers. all works as expected. We
> recently have connected a customer who requires BGP transit from us
> but with a twist.
> 
> The customer for whatever reason do not want their traffic going via
> our preferred provider, is there any way I can force the customers
> outbound traffic to go via my other 2 providers instead?
> 
> I have created the prefix-lists to stop announcing the customers
> routes via the main provider so no traffic should return by them. The
> customer is multi-homed with another transit provider.

You need some kind of source based routing. Policy based routning could
do it, but it's a per hop thing, so all routers from them to the
relevant upstream needs to do it.

Otherwise you could use a GRE tunnel from your customer facing router(s)
(or their CPE(s)) all the way to your edge router(s) towards the
relevant provider(s) and then only policy route on the customer facing
router(s).

If you need to use both providers, maybe you could take advantage of the
CEF recursive lookup and make their next hop (still policy routing) an
address you only see from these two providers and not your preferred
provider.

It would probably be a bad hack though, hard to troubleshoot. If you're
using MPLS VPN you can selectively import relevant default routes into
their VRF, but I guess that's not an option here.

And if you do PBR, any BGP feed you send them will be more or less
useless. Are you perhaps just giving them a default route?

By the way: I'm just guessing, haven't tried it myself.

Regards,
Peter