without wishing to repeat what can be googled for.. putting acls on your edge to protect your ebgp sessions wont work for obvious reasons -- to spoof data and disrupt a session you have to spoof the srcip which of course the acl will allow in Steve On Thu, 31 Mar 2005, Pekka Savola wrote:
On Wed, 30 Mar 2005, John Kristoff wrote: [on bgp/md5 and acl's]
ACLs are often used, but vary widely depending on organization. It can be difficult to manage ACLs on a box with a large number of peers that uses many local BGP peering addresses. I'm sure some organizations reviewed and updated their ACLs as a result of the last scare, but that is a local, private decision and it would probably be hard to get good sample of who and what changed.
I would be double careful here, just to make sure everybody understands what you're protecting.
iBGP sessions? ACLs are trivial if you have your borders secured.
eBGP sessions? GTSM is your friend (if supported). Practically, if you know your peer and you also protect your borders, ACLs are rather trivial as well.
What you seem to be saying is using ACLs to enumerate the valid endpoints for eBGP sessions. That goes further than the above but indeed is also a pain to set up and maintain.
There are other attacks you can make against TCP sessions (protected by MD5 or not) using ICMP, though. (see draft-gont-tcpm-icmp-attacks-03.txt).