GRE tunnel works between routers, not external devices.

maxclark · ‎01-31-2007

Hi all,

I am trying to configure a GRE tunnel between two sites. In my configuration I have three Cisco routers. Router A and Router C are at the first site and are connected directly to each other - Router B is at the second site.

We can create the tunnel between Router A & B no problem. Running an show int tunnel 0 shows the link up. Router A can ping the interface on Router B and vice-versa. However I cannot ping the Router B interface from Router C. I feel like I am missing something basic but cannot identify it.

Relefant configuration and pings/traceroutes are available at the following URL.

Thanks,

Max

http://www.clarksys.com/~maxc/gre.txt

dominic.caron · ‎02-01-2007

You need to add a router to router B

ip route 129.47.255.0 255.255.255.0 tunnel 0

When you did your ping from router A To B, the source of the ping was the ip of the tunnel interface. It was a subnet directly connected to router B so no need for route.