GRE Tunnel

Nov 22, 2005 3 Replies
T

I have the following configuration on my router. Both router A and router B show the tunnel 0 interface is up, line protocol is up. I can ping 172.33.1.14 and 172.33.1.10 from both router A and router B. When I try to ping 172.20.42.17 from router A the ping fails. I can ping



172.20.42.1 from router A (itself) without any problems. The same is true for router B, I can ping 172.20.42.17 (itself), but not
172.20.42.1 the other end of the tunnel.

Does anyone know why the tunnel interface would say up and up but be unable to ping the other side of the tunnel when I can ping both the source and destination addresses of the tunnel endpoints? I can only think that it would be a routing issue but, I'm not sure what I am missing. Any help would be appreciated.



Router A



interface Tunnel0 ip address 172.20.42.1 255.255.255.224 ip pim sparse-dense-mode tunnel source 172.33.1.14 tunnel destination 172.33.1.10



interface Serial0/1 ip address 172.33.1.14 255.255.255.252 ip pim sparse-dense-mode no ip mroute-cache load-interval 30 no fair-queue no cdp enable



ip route 172.20.42.17 255.255.255.255 Serial0/1 ip route 172.33.1.10 255.255.255.255 Serial0/1



Router B



interface Tunnel0 ip address 172.20.42.17 255.255.255.224 ip pim sparse-dense-mode tunnel source 172.33.1.10 tunnel destination 172.33.1.14



interface Serial0/0 ip address 172.33.1.10 255.255.255.252 ip pim sparse-dense-mode no ip mroute-cache load-interval 30 no fair-queue no cdp enable



ip route 172.20.42.1 255.255.255.255 Serial0/0 ip route 172.33.1.14 255.255.255.255 Serial0/0


Thanks, Travis



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N

hi Travis, As far as i know, connected Serial interfaces should be in the same subnet to have direct connectivity. But u can try to set the routes through the tunnel interface.

sth like that

ip route 172.33.1.14 255.255.255.255 172.20.42.1

regards, sebastian

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T

Sebastian,

I guess I forgot to say that these two routers are connected through MPLS cloud. They are not directly connected. I do have connectivity because I can ping through the cloud but, I cannot use the tunnel addresses to ping each other. Thank you for your response.

Also the route that you put in down there looks like it would cause the endpoint of one of the the tunnel to go through the tunnel itself. I thought that this was something that shouldn't be done. Doesn't this cause some recurive routing errors?

Thanks, Travis

snipped-for-privacy@googlemail.com wrote:

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