Re: Inter-AS option naming confusion

Thanks! I had a feeling this was the case, but I wanted to make sure. I
knew that 1, 2 and 3 were the same as A, B and C, but then I was thrown off
when I saw a site talking about 10B. Then another site was talking about
suboptions for option 2, and it had suboptions 2a, 2b, and 2c. lol I just
wanted to make sure I kept it straight in my mind.

I guess that makes sense about Option A not having its own configuration
guide in the MPLS section since there is no MPLS between the ASes. It's
basically two ASes running intra-AS L3VPN and then with VRF lite between
them, right?

Thanks again,
John

On Mon, Jan 21, 2013 at 9:00 AM, Brian McGahan <bmcgahan_at_ine.com> wrote:

> 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 - 09:30:46 ART