EIGRP over GRE tunnels

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Aug 6th, 2009
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      i have 2 sites connected using different ISPs, we configured EIGRP over GRE tunnel.

when one of the 2 links are down , the traffic not affected.

when the other go down , the two GRE goes down

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John Blakley Thu, 08/06/2009 - 06:55
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I'm not sure that I understand the problem, but here's my take on it. You have this in your routing table:

D [90/297372416] via, 00:10:28, Tunnel1

[90/297372416] via, 00:10:28, Tunnel2

for the same destination. When one of your links goes down, and you look at the routing table, chances are the other link is still up and routing through that tunnel to get to the same destination. That would explain why you have to bring both sides down because now your other destination doesn't know how to get to it either.



Peter Paluch Thu, 08/06/2009 - 12:04
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Can you please post the show ip route output of both routers when you shut down the s0/0/1 interface on NIB_Router_BabElouk and both tunnels go down?

I am suspecting a tunnel endpoint reachability problem here but I need more information about it.

One more question: Why are the corresponding Frame Relay subinterfaces on both routers not in the same IP subnet? For example, on NIB_Router_Maadi, the s0/0/0.16 is while on NIB_Router_BabElouk, the s0/0/0.16 is, thus they are in two different networks ( and, respectively). Why is that? I assume that there is a PVC going directly from one interface to the other - no intermediate router inbetween. Can you confirm this?

Best regards,


ibrahim_hassan Sat, 08/08/2009 - 01:43
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Peter ,

there is ISP devices between the two sites so there are two different subnets (point-point).

Peter Paluch Tue, 08/11/2009 - 00:33
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I am sorry for replying lately. Can you please post the output of the show ip route commands on both routers after you deactivate the s0/0/1 interface on NIB_Router_BabElouk and both tunnels go down, as I originally asked?

Best regards,


Peter Paluch Thu, 08/13/2009 - 13:46
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Thank you for your reply and please excuse me for getting back to you so lately.

The second file contains only the output of the NIB_MAADI router. I was looking also for the NIB_Router_BabElouk routing table in the moment.

Can I please ask you once more for these data? To have as much usable information as possible, please, follow this sequence:

1.) Shutdown the s0/0/1 interface on NIB_Router_BabElouk (not on the other router!)

2.) Wait until the EIGRP session goes down and then capture the output of the following commands on both routers:

terminal length 0

show ip route

show ip eigrp nei

show ip eigrp interface

show ip int brief

show interfaces

show frame pvc

show frame map

Sorry for still requesting new information but it is important to me to see in more detail what is really going on there.

Best regards,



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