Question on extending VLAN over GRE tunnel

Unanswered Question
May 16th, 2008

Dear NetPros,

Since GRE is a layer3 technology would it be possible to use it to extend a vlan from one location to the other side of the tunnel which is in a separate geo location? I'm not interested in using L2TPv3 because it doesn't support 6500 platform.

Thanks in advance!

I have this problem too.
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Richard Burts Fri, 05/16/2008 - 11:25


Extending the VLAN over a GRE tunnel would require bridging the VLAN and carrying the bridged traffic over the GRE tunnel. This is not a supported implementation.

You can enter the configuration commands and they are accepted (they are not an error - at least not the last time I tested it). I have heard people say that they have configured this and that it passed traffic. However Cisco does not support it. If you try it and something unusual happens Cisco will not help you fix it.



Yang Xia Mon, 05/19/2008 - 09:16

Thanks Rick for your replying. Do you mean using the vlan bridge group over GRE tunnel? I haven't seen any document in CCO and won't be surprised that is not supported feature by Cisco.

Giuseppe Larosa Sat, 05/17/2008 - 11:12

Hello Yang,

if you cannot use L2TPv3 could EoMPLS be a viable option ?

You can ask your provider for EoMPLS services.

In a MAN context just Q in Q tunneling is a good solution (double 802.1Q tagging).

Look for metro ethernet solutions on the CCO

Hope to help


lamav Sun, 05/18/2008 - 16:13


Is using VPLS (layer 2 VPN) solution an option for you?


Yang Xia Mon, 05/19/2008 - 09:09

Hi Victor,

Thanks very much for replying.

My situation is I have a single network to be extended to the data center where the VM cluster locates. I doubt layer2 VPN will work in this scenario. But I'll keep it in mind.



lamav Mon, 05/19/2008 - 10:02


When i asked if you think this could be a solution for you, I was talking more in terms of cost, planning, authorization and approval from your management, etc.

I wasnt questioning the technical feasibility. A layer 2 VPN is meant to do exactly what youre talking about: extend a layer 2 domain/vlan across the public network over an MPLS cloud.



Yang Xia Mon, 05/19/2008 - 10:50

To use the VPN MPLS technology, ISP has at least to setup their own MPLS cloud and assign RTs to the routes. This approach isn't just feasible for me at this time. Thanks for the thought. I was looking for a quick GRE related approach to extend the VLAN to the VM cluster.



lamav Mon, 05/19/2008 - 11:45

So what youre saying is that your provider either doesnt provide MPLS as a service offering or your organization is not ready for that commitment.


Good Luck.


Yang Xia Mon, 05/19/2008 - 12:32

yes you're right Victor. My ISP isn't ready for full blown MPLS applications. In the mean time I need a quick solution without adding another circuit for the virtual servers to be on the same local vlan.


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