Paul Stewart wrote:
What is common practice for this scenario? We would still prefer to just send a full table and put the control into their hands but I'm also concerned if they will have the technical expertise to accomplish this.. On their side, what would be common practice? I've been looking at conditional BGP advertisements using route-maps but don't believe that's the best solution..
They can control their outbound fairly easily. They should make sure they're getting the same level (default-only, partial, full) of routes from you as from Cogent - if they take more from you, those routes are more-specific and would win regardless. I'd suggest they take default-only from you (or more but filter out everything but default so they can change on the fly later) and whatever they wish from Cogent.
Controlling inbound is often tougher. Any smart provider sets a higher local pref on customer routes than on transit/peer routes (make money rather than pay money), so if you do this you'll need to make an exception for them (or offer the exception via communities). Otherwise, you'll prefer their announcement no matter how many prepends they do, and if that happens for a minute, your transits will likely prefer your propagation no matter how many prepends they do. Even if you don't do this today, if Cogent goes down, you'll choose the direct link (it's the only one live) and your transits will do the same thing (your routes have customer LP in their network). When Cogent comes up, your transits will ignore the Cogent-propagated route since it's only peer LP. They'd have to bounce the link to you to restore their preferred balance. You'll need to find out how to accomplish the same thing in your providers' networks as well. (Been there, done that, got the t-shirt.)
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