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Community Member

Cannot ping tunnel source for GRE tunnel

Router A

Interface tunnel 0

ip address 172.16.1.1 255.255.255.252

tunnel source a.b.c.d

tunnel destination e.f.g.h

Router B

Interface tunnel 0

ip address 172.16.1.2 255.255.255.252

tunnel source e.f.g.h

tunnel destination a.b.c.d

Over router A, I can ping 172.16.1.2 but cannot ping 172.16.1.1. After 30 minutes, I can start pinging 172.16.1.1 but cannot get 100% reply. If I use tunnel mode ipip, I can ping 172.16.1.1 instantly. or if I use routing protocol with neighbors concept like eigrp/ospf, I can ping 172.16.1.1. if I use rip, I cannot ping 172.16.1.1.

Over router B, same thing happen, I can ping 172.16.1.1 but cannot ping 172.16.1.2 when I use GRE encapsulation.

Why?

5 REPLIES
Community Member

Re: Cannot ping tunnel source for GRE tunnel

I wish I had an answer to your question but instead I am wondering where you found the information to configure your routers for the GRE tunnels. I am looking to do the same thing here but for some reason I am not finding the right document to help me out!

If you could help, that would be great!

James

Community Member

Re: Cannot ping tunnel source for GRE tunnel

Community Member

Re: Cannot ping tunnel source for GRE tunnel

Not being able to ping the local GRE interface was a known bug in the past (not sure if it has bee resolved or not). But if you can ping across the tunnel, sounds like the tunnel is fine.

Community Member

Re: Cannot ping tunnel source for GRE tunnel

I have had a similar problem, but it doesn't matter, you are trying to ping a virtual interface on your current router, pinging the other end of the tunnel and issuing the command sh int tunnelx of your current router would show the tunnel is up, and I assume that is what you are trying to do. The best test is telent to router2, configure a loopback interface, address it as anything, go to router1, configure a static route>> ip route (address of loopback on router2) tunnel x (this route says to get to the loopback interface, go into the tunnel, if you can ping the loopback you definitely have a GRE tunnel.

Community Member

Re: Cannot ping tunnel source for GRE tunnel

Checkout bug CSCdr36482 - I've been having the same problems.

Try moving the tunnel config from Tunnel 0 to Tunnel 1 on both routers- I know it sounds strange but i've had some sucess doing this.

Sometimes just deleting and re-adding the tunnel interfaces cures the problem.

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