[nsp] ibgp across wan - BCP ?

[Pete Templin]

The underlying IGP will take care of next hop reachability if you use loopback.  If it's an island router with respect to your IBGP topology, it probably doesn't matter, but if its multihomed within your IBGP mesh you probably want to peer using the loopback.

In our case, we recently migrated to BGP confederations.  We have four cities, and presently one router per city but that's likely to explode soon in our bigger cities.  Each city is now its own confederation.  To me, it makes the decision quite clear: intra-city is true IBGP, so the routers will peer by loopback. Inter-city is logically EBGP, so the routers peer by interface address.  This makes it easier to adjust MED based on the IGP metric or a similar comparison.  With all due credit, http://www.nanog.org/mtg-0006/confed.html was the inspiration for us to make the switch, and by all accounts it's best to move to confederations earlier rather than later. 

Pete Templin
Senior Staff Engineer
TexLink Communications
(210) 892-4183
pete.templin at texlink.com


-----Original Message-----
From: matthew zeier [mailto:mrz at intelenet.net]
Sent: Tuesday, December 02, 2003 12:26 PM
To: cisco-nsp at puck.nether.net
Subject: [nsp] ibgp across wan - BCP ?


Across a WAN link, is it common or BCP to peer with an iBGP peer through the
loopback address or the interface address?

RouterA ------ RouterB (route-reflector)


RouterB has a bunch of other iBGP peers and they all peer with their
loopback address.  RouterA is on the other end of a PTP link.


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

_______________________________________________
cisco-nsp mailing list  cisco-nsp at puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/