RE: VPC layer 2 extension between data centers

This is a normal validated design actually: http://imgur.com/2ILkATY

See "Cisco Data Center Interconnect Design and Implementation Guide"
http://www.cisco.com/en/US/solutions/collateral/ns340/ns517/ns224/ns949/ns304/ns975/data_center_interconnect_design_guide.pdf

VSS will support the same design here as vPC, but vPC has better support for split-brain detection during certain corner-case failure scenarios. If designed properly -operative word being *if* here :) - you should not get a layer 2 loop like Marc mentioned. Of course whenever you span the layer 2 domain you also span the failure domain, so you have to make sure all your ducks are in a row with things like your root bridge placement, root guard, bpdu filters, bridge assurance, etc.

It would ideally be a better design to do this with OTV vs. Back-to-Back vPC, because OTV has special enhancements specifically for the DCI, such as termination of the STP domain, layer 2 filtering capabilities, ARP caching on the edge, etc. Your limiting factor will be though that OTV isn't supported on Nexus 5K, only 7K. Another option would be to dedicate a separate platform to it, such as ASR 1002, etc. The drawback of going to N7K or ASR of course then is the cost.

So long story short, yes you can do back-to-back vPC for this design and it will work.

HTH,

Brian McGahan, CCIE #8593 (R&S/SP/Security), CCDE #2013::13
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 marc abel
Sent: Tuesday, March 19, 2013 11:41 AM
To: Viet-Hung TON
Cc: Cisco certification
Subject: Re: VPC layer 2 extension between data centers

This is technically feasible, but sounds like a truly awful idea to me.
Rather than adding redundancy you are turning both data centers into one giant failure domain. I just saw a layer 2 loop wipe out an entire data center, with this solution you could wipe out both.

My $0.02 cents.

-Marc

On Tue, Mar 19, 2013 at 10:16 AM, Viet-Hung TON <vton_at_integra.fr> wrote:

> Hi all,
>
> Do you have any experiences about using VPC to connect between two
> data centers in different geography? I plan using 2 nexus 5000 each
> site fo redundancy, the connections are based on physical dark fibers
> WDM. The latency between 2 sites is around 1.5 - 2 ms. Otherwise, the
> VSS runs well in this case?
>
> Thanks for your share.
>
> Viet
>
>
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--
Marc Abel
CCIE #35470
(Routing and Switching)
Blogs and organic groups at http://www.ccie.net