[c-nsp] Limiting upstream paths to downstream customer - BGP

[Paul Stewart]

Hi there.

 

I'm looking for a Cisco doc or a quick guide to *best practice* for the
following scenario:

 

Provider A gets 5 upstream BGP feeds via two core routers.

Provider B wants to purchase transit from Provider A but does not want to
send/receive any traffic via one of Provider A's upstreams (Provider X in
this case).

 

Provider A also uses BGP communities to mark their downstream customers,
their upstream connections etc.

 

Obviously Provider A can simply not announce Provider B to Provider X
solving this issue in one direction. but what about traffic coming into
Provider A from Provider B that prefers Provider X outbound?

 

I'm thinking that you could use route-maps on Provider A (which would
already be in place anyways most likely) and local-pref Provider X's routes
specific to Provider B's community?  If this is the best practice, anyone
have a config snippet they could share or is there is a better way?

 

Thanks in advance, hopefully I'm explaining this well.

 

Paul