[nsp] conditional BGP config - help

[matthew zeier]

I have three transit providers - A, B, C - and want to setup conditional BGP
advertisements such that I only advertise my routes to C is both A and B are
down.

I'm not clear on how to setup the non-exist-map.  The only routes that I
think I can base my condition on are the transit interfaces and the /30
networks.  However, I can't figure out from the docs
(http://tinyurl.com/3gbrl) if the non-exist-map is either-or or whether both
have to match for the condition to be true.

Is it easier/better to match on the as-path instead of the transit
interfaces?  Something like:

ip as-path access-list 1 permit ^ASN-of-provider-A
ip as-path access-list 1 permit ^ASN-of-provider-B

neighbor 10.10.10.1 advertise-map ADVERTISE non-exist-map NON-EXIST

route-map NON-EXIST permit 10
 match as-path 1


?

Thanks.

--
matthew zeier                        | "Nothing in life is to be feared.
InteleNet Communications, Inc.       |  It is only to be understood."
(949) 784-7904                       |       - Marie Curie