RE: Inter-AS option naming confusion

The naming convention comes from RFC 4364, "BGP/MPLS IP Virtual Private Networks (VPNs)" (http://tools.ietf.org/html/rfc4364#section-10)

Normally they are referred to as Option A, Option B, and Option C, but Option 10A/10B/10C would be referring to Section 10 in which they're referenced in the RFC, so it means the same thing.

Option A is back-to-back VRFs, which just means that each provider treats each other as a customer. This is the simplest but least scalable design, and the most commonly implemented one in my experience. Option A doesn't have a section in the configuration guide because implementation-wise it's the same as a normal Intra-AS L3VPN config.

Option B is direct EBGP VPNv4 peerings between the AS edge routers.

Option C is multi-hop EBGP VPNv4 peerings between Route Reflectors (typically), and an IPv4 Unicast + Label EBGP peering between the AS edge routers.

Option AB I believe is Cisco proprietary only. This is when you have a single VPNv4 peering between the AS edge routers (like option B), but the next-hops point at separate sub-interfaces that are in different VRF tables (like option A). This way you get the simplicity of back-to-back VRF exchange, but only need one control plane session to carry the routes between the AS edge routers.

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 John Neiberger
Sent: Sunday, January 20, 2013 7:38 PM
To: ccielab_at_groupstudy.com
Subject: Inter-AS option naming confusion

I'm a little confused about the naming (or numbering) conventions used to describe the various inter-AS options. I've seen them numbered, like Option1, Option 2 and Option 3. I've seen them called Option A, B and C.
Just today I saw some that were called Option 10A, 10B, etc. And then I saw a new one today called option AB that I had never seen before.

Can someone clarify the nomenclature here?

Also, what does Cisco call Option A (back to back VRF)? I can't find the configuration guide in the 12.2SR configuration guide library. They only seem to list Option B, Option C, two CSC configurations and then Option AB, but apparently no Option A. I can only assume that they have titled it in a way that I don't recognize.

Thanks,
John

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Received on Mon Jan 21 2013 - 10:00:05 ART