Unanswered Question
Feb 22nd, 2008
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I am providing a backup solution for a customer. Right know there is a device between ME and the WAN that is out of my control. In order to run a dynamic routing protocol I have established GRE tunnels between myself and the head end device. I am then running EIGRP and am getting all of the required routes except the default route, so I redistributed JUST the static route using a route map. I can see the static route in eigrp when I do a show ip eigrp topo. Next I remove the static I have pointing to the physical interface. Almost immediately my tunnel goes down and I lose all of my eigrp routes. It logs an error "%TUN-5-RECURDOWN" error. I found a document (22327) that says in order to remedy this use a static pointing to the interface. The problem with this is that the WAN circuit (which my device has no visibility into) can go down and the GRE tunnel is still up. This causes my device to still consider the a valid route.

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Edison Ortiz Fri, 02/22/2008 - 08:43
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What you are seeing is normal. You can't learn the destination IP of the tunnel via the tunnel.

When you configured the tunnel, you needed to create a destination tunnel ip, this IP must be reachable via the physical interface or any other interface but not the tunnel interface. If you want the default route via the tunnel, create a host route to the destination tunnel IP via the physical interface and the default will automatically be learned via the tunnel with EIGRP.




Richard Burts Fri, 02/22/2008 - 08:44
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There are some aspects of your description that I do not understand well. But it seems to me that a solution for your problem is to configure GRE tunnel keepalives. By default GRE tunnel interfaces do not do keepalives (as part of being a virtual interface and keepalives are usually for physical interfaces). But Cisco introduced (somewhat recently) the keepalive function on GRE tunnels as an option. Assuming that you are running code that supports it you can configure keepalives on the tunnel interfaces and they will detect a failure to transmit through the tunnel and will take the tunnel interface to line protocol down. This would cause the static route to become invalid.



Mohamed Sobair Fri, 02/22/2008 - 09:57
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This is a tunnel recursion error, its common if you set the tunnel destination as the remote tunnel ip.

Pls make sure the tunnel source & destination are not the tunnel interface addresses.




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