The MPLS-OPS Archive

[Ran Liebermann <ranmails@gmail.com>]

Greetings,

I've just encountered a problem, for which I found a workaround, but I
still would like to configure it as I wanted in the first place.

Please see the following diagram:

CE --- AS1_PE --- AS1_P --- AS1_ASBR --- AS2_ASBR --- AS2_P --- AS2_PE --- CE

Let's say I'm running AS2, and everything currently works well.
Now I want to configure the IGP of my AS to carry only the loopbacks
of my network (and ofcourse also the connected interfaces on which the
IGP is running), and the iBGP to carry all the redistributions of
static and connected routes.
When I do that, the /32 route of the next-hop in AS1 becomes a BGP
recursive route, pointing to the loopback of AS2_ASBR, instead of
pointing to the other side of the LSP that instructed the packets to
be carried out of my ASBR to AS1_ASBR.

When this recursive route happens, then if I try, for example, to do
"show mpls for vrf X <prefix>" then I see the outgoing label is the
same as the loopback of AS2_ASBR.
When the packet arrives at AS2_ASBR (without the outer label) then the
inner label is acted upon, and although the label is identical to the
label that AS1_ASBR is waiting for, AS2_ASBR doesn't know this label
(or has some other prefix for it) and carries it to a different place.

My question is - is it possible to configure this? when I want BGP to
carry the next-hop of the other AS?

Thanks,
--
Ran.

P.S.: The workaround was to configure the interfaces towards AS1 to be
carried in the IGP.

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