Strech VLAN's from different VDC's over OTV

MARK THYS · ‎05-19-2016

Hello everybody,

I've a customer case with two DC's where we use OTV as DCI.

Each DC has two N7K with four VDC's named Prod, FCoE,DMZ and PoC.

We want to stretch the VLAN's from this four VDC's over OTV.

But on the Cisco documentation, I can't find any config example or information.

Does have anyone have experience with that?

Do I have to configure one Overlay interface per VDC with separate MC addresses?

Or is one Overlay interface sufficient and just try to avoid duplicate VLAN ID from all the VDC's

Thanks for every reaction.

Warm Regards, Mark

jeestrad · ‎05-19-2016

Hello Mark,

Answering your questions:

We do have a sample configuration showing step-by-step procedure to setup OTV:

http://docwiki.cisco.com/wiki/Nexus_7000_-_OTV_-_Design_and_Configuration_Example

About your questions on the Overlay interface:

The "Overlay interface" is responsible to establish the Tunnel between sites, sitting "above" the "Join Interface", which is the physical Interface connecting to the other Site(s). This Overlay interface only exists in your OTV VDC, which, preferably has to be purely configured for this. Other consideration to take in account is that if your N7k is the Gateway for you in-site VLANs you cannot configure OTV in the same VDC. Expanding on the Overlay and VLANs, if you configure High Availability on any given site by having 2 OTV VDCs (one per N7k). you need to configure 2 things, the Overlay interface, and a Site VLAN, which allows for OTV to know which peers belong to the same site. This site VLAN has be to allowed within the site (and not across OTV), so the Overlay Interfaces in the site can reach each other. Other things to consider are the Control plane communication, either in Multicast or Unicast, which depends if your Transport Network supports multicast, the configuration changes a bit if multicast is not supported. Another thins to take in account is FHRP (i.e. HSRP) each site has to be isolated if the associated VLANs are extended over OTV, this is done by blocking the HSRP messages from passing through the tunnel, More of this in the next link:

http://www.cisco.com/c/en/us/products/collateral/switches/nexus-7000-series-switches/white_paper_c11-644634.html#_Toc408469214

I hope the information could clear up some of your doubts.

-Enrique

MARK THYS · ‎05-20-2016

Hi Enrique,

First thank you to responding to my question.
I already have some practical experience with OTV as DCI.
So with the configuration of that, I've no problems.
But it was always one VDC in the aggregation tier,
where I needed to stretch the VLAN's over OTV.

But with this new customer case,
there are several VDC's in the aggregation tier where the VLAN's have to be stretched over OTV.

In the sample document you presented, you can clearly read the next quote:

"It should be noted that in a multitenancy environment,
the same OTV VDC can be configured with multiple overlays to provide a segmented Layer 2 extension for different tenants or applications.
It should also be noted that when multiple data center sites are interconnected,
the OTV operations can benefit from the presence of multicast in the core".

So my question is, do I need one Overlay interface for all the tenancy VDC's,
or one Overlay interface per tenancy VDC.
And in the case of multiple Overlay interfaces,
what's the proper way of setting up the MC addresses.
And what's the advantage or disadvantage of using one Overlay interface for all the VDC's together.

Regards, Mark

sudkamt · ‎06-14-2018

Hi Mark,

Have you got answers to your queries? I am also facing similar scenario now, please share your response.