VRF forwarding on subinterfaces

Unanswered Question
Feb 9th, 2007

Is it possible to run the VRF's over subinterfaces.

I want a PE which will be connected to a L2 switch on a dotq trunk and will have two subinterfaces corresponding to 2 customers to forward the traffic out the proper sub interfaces.

The switch is a pure L2 switch and is not possible to run VRF lite on it.

The setup works perfectly when both the customers are terminated on different LAN interface.

Is there any special configuration required to make this work with subinterfaces?


I have this problem too.
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Michael Odom Fri, 02/09/2007 - 22:16

There shouldn't be anything special, just run the ip vrf forwarding command on the sub-interface.

I have this configuration in my network using 3700 and 3800 routers, and Cat6K/Sup720, with no issues.

mohammedmahmoud Sat, 02/10/2007 - 03:04

Hi Narayan,

I agree with Michael, there shouldn't be anything special, we have this setup in production using 7204VXR (NPE-300 and NPE-G1) and Cat6K/Sup2 with no problem, try to investigate your IOS feature set.



royalblues Sat, 02/10/2007 - 05:35

Thanks for the inputs.

I had tried this setup on dynamips and the moment i added the the 2nd subinterface, it broke everything.

Mohammed / Michael, are you sure you are not running VRF lite on the CAT6K cos the switch i ahev shown in the diagram is a 2950 L2 switch


mohammedmahmoud Tue, 02/13/2007 - 00:42

Dear Narayan,

You shouldn't need VRF lite on the switch (it should be a pure layer 2 switch), this setup is up an running in our in production network without any problems, kindly check your PE IOS most probably it is the problem.

CE(neither VRF nor VLAN aware) --> L2 switch (with VLAN per customer and dot1q trunking with the PE) --> PE (dot1q subinterface per customer with the ip vrf forwarding command under it).




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