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Re: iBGP next hop and multi-access media

  • From: John M. Brown
  • Date: Tue Oct 08 10:03:06 2002

Let me see if I got this.

Route A:
	unknown networks behind it
	uses as a neighbor to router B

Router B:
	has a network  172.16.16/24 
	uses as a neighbor to router A.

Router A's table shows
	172.16.16/24  ->

You want Router A to ARP and pretend its on the local
broadcast domain for the 172.16.16/24 prefix.

But that prefix is NOT local to router A, thus it must
ROUTE and thus uses  the NexHop in its table.

It seems you description is wrong....  But I don't know..

Please clarify

On Sun, Oct 06, 2002 at 12:44:07PM -0400, Ralph Doncaster wrote:
> Background: 
> Router A and B are connected via a common ethernet segment 1. Router A
> uses, and Router B uses Router B also has
> another subnet configured for ethernet segment 1;
> When I setup a situation like the above, with Router B advertising the
> to router A, router A sees a next hop of  This
> is not good since packets from A going to the 172.16.16 subnet get sent to
> Router B, which then ARPs the desitnation, instead of just being ARPed by
> router A.
> I don't want to turn on ICMP redirects on B since they're insecure and
> ugly.  I've also made sure I'm not using next-hop self.  Is there a way to
> make this work?
> Ralph Doncaster
> principal,