Task 4.1 MPLS VPN

I see that it works, but I don't understand why. How does this work after adding the tunnel interfaces on R1 and R2 to a VRF instance? I'd appreciate your input. I'd like to understand how the configuration on this task works. Thank you.


  • by issuing ip vrf forwarding <vrf name> you assign interface to particular virtual routing table.

    It works just like with physical interfaces, with no difference.

    Note that even if tunnel endpoints are in global vrf, tunel traffic itself can be assigned to other vrf, just like in this case.

  • Hi,

    Like riozavarce, I too don't quite understand how this works.

    The tunnel endpoints on each interface are in the global routing table, so I can understand how the tunnel has been setup.

    But the route distinguisher for the VRF on each router has to be different. I know, because I've tested it.

    Could somebody explain this further?

    Many Thanks

  • Hi Tommey,

       The SG uses a different RD value on the two routers; however for VRF lite(no MPLS) , which is the case in here, you don't care about RD values, as these are not being used. Most of the routers will let you create and use a VRF without even configuring a RD value.

    Good luck with your studies!

  • Thanks for your reply Cristian.

    I did some testing with the same RD value on each router. If the RD values are the same on each router, then the tunnel endpoints are unable to ping each other. With different RD values configured on each end of the tunnel, the tunnel endpoint can ping each other. I agree the RD values don't actually matter, but it has to be configured and it has to be different on each endpoint router.



  • Hi Tommey,

        I don't even try to make the test out; with only VRF-lite involved, the RD values are not propagated, so are only locally significant, also are not even required to be configured. You should get connectivity with VRF lite, regardless if you have the same RD values, different ones, or no RD values. From a technological point of view, this is how it goes.

    Good luck with your studies!

  • Hi Tommey,

    I don't have the lab with me now but if task is asking to configure only VRF-Lite, it should work without RD as well. So it doesn't matter what RD value you use in both site.

    Some example of VRF-lite without RD here:




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