Interface Tunnel show up on onside only but routing traffic

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Oct 8th, 2007
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I have 2 7206VXRs with Tunnel interfaces configured. One side of the tunnel is mapped to a Serial interface and the other side is mapped to an Multi-link T1 bundle. The MU tunnel interface is showing up/up but the serial interface is showing up/down. Traffic is being routed across the interface. Is this cosmetic?

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Richard Burts Mon, 10/08/2007 - 10:34
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There are parts of your question that I do not understand. Let me address the part that I think I do understand and if my answer does not resolve your question then perhaps you can clarify.

When you say tunnel interface am I correct in assuming that we are talking GRE tunnel rather then VPN tunel or something else?

With GRE tunnels the IOS will show the tunnel as up up as long as the router has a viable route to the tunnel destination (unless you have configured the optional GRE tunnel keepalive).

If the serial interface is showing up/down then that is not cosmetic as far as the serial interface is concerned. It means that keepalives have failed on the serial interface and that no traffic is being sent over the serial interface. It may or may not affect the tunnel that the serial interface is not working. As long as there is a viable route toward the tunnel destination then the tunnel itself may work. If I understand the end of your question it does seem to be saying that traffic is going through the tunnel. Am I correct in understanding that?




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