[c-nsp] Finding AS Edge Intefaces

[Tony Tauber]

For a bunch of different purposes, it seems useful to be able to
detect which interfaces represent the "edges" of an Autonomous System
and which neighboring ASN lies across the link.

For cases where we're interface peeering using BGP, it isn't too hard
to line up which neighbor IP addresss is related to which interface
using the address and mask of that interface.  (Though this logic
could be simpler, IMHO.)

Where it's tougher is when using loopback peering with eBGP multi-hop
over parallel links for load-balancing.

Anyone have a programmatic way to derive these relationships either by
examining the config (preferable) or the state of the router (CLI or
SNMP) or a combination of the two?

TIA,

Tony