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New Member

Interface Tunnel


We run up to 3 tunnel interfaces on our main 7206 router for some smaller ISP in the country. Now we encounter the following problem: after a few days ( random time ) the tunnel interfaces start to drop packets ( I saw that in show interface tunnel X in the input queue line ) and after a clear interface tunnel X, everything comes back to normal.

The tunnel interfaces are in mode gre, mtu set to 1500.. nothing else.

One thing could be we do not use the primary ip address of the real interface (fastethernet) .. could this be a problem? (we use a secondary one).

And also could anyone tell me what to debug in this case?


Teodor Iacob


Re: Interface Tunnel

Often times complex troubleshooting issues are best addressed in an interactive trouble-shooting session with one of our trained technical assistance engineers. While other forum users may be able to help, it’s often difficult to do so for this type of issue.

To utilize the resources at our Technical Assistance Center, please visit and to open a case with one of our TAC engineers, visit

If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.

New Member

Re: Interface Tunnel


Not sure if you got this fixed but..

I have a few 7206VXR's using multiple tunnels. I sometimes use loopbacks as tunnel source and destination rather than physical addresses. Also there was an issue with the MTU size with GRE encapsulation as the MTU exceeded the Interface MTU. i cannot recall the software release now but if you have a fairly new IOS image it should be OK else you could fix the MTU at a different size. e.g

interface Tunnel0

description GRE Tunnel0 corpa to RSM via Gi

ip address

ip mtu 1600

tunnel source

tunnel destination

Hope this helps.