Can't connect to local devices with GRE tunnel

[oyvind.roa.hatlestad]

I’m trying to configure 2 routers and fuse the local networks. I have connected the routers together with fiber, and configured an GRE tunnel. Both routers can ping each other on the GRE tunnel and on the local connection. But from the one router I can’t ping any devices on the other routers local network, I think the problem is routing. But I can’t find the problem.

I have an DHCP server running in one of the networks. I have configured routing on the other network router so this works. I can supply IP addresses in to the other network.

Anyone have any clue on what it is that I’m missing?

I'm using Cisco 2811 Routers

I'm putting the running config on both routers as attachments

[chrihussey]

If the only connectivity between the two routers is the GRE tunnel you can't have the same networks on each router (10.0.2.x & 10.0.3.x). 

[oyvind.roa.hatlestad]

Okey :) So it’s not the best way to use an GRE tunnel to fuse the network? When the DHCP server on the one side?

[Richard Burts · Accepted solution]

Where the DHCP server is located is only a small part of the problem. The more important part of the problem is the need to have the same networks (10.0.2.0, 10.0.3.0) at both sites and to need to "fuse" the networks. GRE will not do that. The GRE tunnel creates a layer 3 hop between the sites and does not support having the same networks/subnets at both sites.

If you really need to fuse the networks then you need to look into something like L2TPv3 which is a technology that does support connecting the same subnets/networks at different sites. A better solution would be to have one set of networks/subnets at one site and a different set of networks/subnets at the other site.

HTH

Rick

[Richard Burts]

I am glad that my explanation was helpful. Thank you for using the rating system to mark this question as answered. This will help other readers in the forum to identify discussions that have helpful information. These forums are excellent places to learn about networking. I hope to see you continue to be active in the forums.

HTH

Rick