RE: MPLS Inter-AS Option A using OSPF (capability vrf-lite)

If the route is Inter-Area (LSA 3) to begin with, it will be External (LSA 5) on the other site. If you want it to be LSA 3 on the other site then it needs to be Intra-Area (LSA 1) to begin with. You can use a sham-link to maintain the route as Intra-Area over the MPLS backbone, but there's really no clean way to do what you're trying to.

HTH,

Brian McGahan, CCIE #8593 (R&S/SP/Security)
bmcgahan_at_INE.com
 
Internetwork Expert, Inc.
http://www.INE.com

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of Tom Kacprzynski
Sent: Friday, March 08, 2013 9:32 AM
To: Cisco certification
Subject: MPLS Inter-AS Option A using OSPF (capability vrf-lite)

I was playing around with MPLS Inter-As option A (back to back vrf) and wanted to lab all routing protocols that are used between the ASBRs on their respective subinterfaces. I used eBGP, EIGRP and OSPF. I had some problems with OSPF where I could not get the LSA 3 to be reassembled at the other end of the VPN. This leads me to a very specific question: When using OSPF in Inter-AS Option A, is it possible to reassemble the internal OSPF (LSA 3) route on the other end of the VPN? I've tried it with EIGRP and that worked but with OSPF I only see External LSA 5 routes.

Here is a sample topology:

CE--(OSPF)---PE----*(AS1)*----*ASBR1---*(OSPF)*--ASBR2*---*(AS2)*
---PE---(OSPF)--CE

I know that usually you would use eBGP as the routing protocol between the ASBRs but I wanted to try using OSPF. The problem I'm encountering has to do with "capability vrf-lite" on the PEs. When I enter that command on one ASBR it doesn't reassemble OSPF routes as LSA 3 but as LSA 5. I've checked the domain ID and they are matching.

Based on my observation it looks like when you apply the "capability vrf-lite" command on a PE(in this case the ASBR), it will always redistribute OSPF routes as external LSA 5, no matter what domain-id you are using.

Capability vrf-lite is usually used on CEs that have OSPF running on vrfs.
When enabled, it disables checks like for Downward bit and domain tag.
Looks like another feature of this is to always redistribute M-BGP routes as External LSA 5, even if domain ID matches and extended communities are propagated.

Has anyone seen something like that?

Thanks

Tom Kacprzynski

Blogs and organic groups at http://www.ccie.net
Received on Fri Mar 08 2013 - 10:24:04 ART