For some IETF work in progress related to Source Address Validation (SAV), it
is useful to know the purposes for which NO_EXPORT may be attached to routes
announced in BGP, especially towards transit providers?
I know it makes sense for an AS to announce an aggregate less-specific prefix
to transit providers and peers without NO_EXPORT while announcing some
more-specific prefixes (subsumed under the aggregate) with NO_EXPORT towards
customer ASes. But are there good reasons when an AS might announce a prefix
(route) to a transit provider with NO_EXPORT attached? The IP address space in
consideration here is meant to have global reachability.
It is also used to manage some aspects of inbound traffic flow,
especially when you are peering just for "my customers to talk to your
customers."
:-) /r
