RE: Inter-AS option naming confusion

Another good reference for this is the "MPLS Configuration on Cisco IOS
Software" book, although he refers to Options A, B, and C as Options 1, 2, and
3.

http://my.safaribooksonline.com/book/networking/mpls/1587051990/inter-provide
r-vpns/ch07lev1sec1

> It's basically two ASes running intra-AS L3VPN and then with VRF lite
between them, right?
Yes. The key is that in Option A the Inter-AS link is not MPLS enabled, and
traffic is sent as regular IP. In Options B and C the Inter-AS link sends
MPLS labeled traffic.

HTH,

Brian McGahan, CCIE #8593 (R&S/SP/Security)
bmcgahan_at_INE.com<mailto:bmcgahan_at_INE.com>

Internetwork Expert, Inc.
http://www.INE.com

From: John Neiberger [mailto:jneiberger_at_gmail.com]
Sent: Monday, January 21, 2013 10:31 AM
To: Brian McGahan
Cc: ccielab_at_groupstudy.com
Subject: 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<mailto: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<mailto:bmcgahan_at_INE.com>

Internetwork Expert, Inc.
http://www.INE.com

-----Original Message-----
From: nobody_at_groupstudy.com<mailto:nobody_at_groupstudy.com>
[mailto: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<mailto: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 - 10:50:34 ART