Hey I'm trying to setup a GRE tunnel in a test setup and I just had a few questions.

Do both end points on a gre tunnel have to be on different subnets?

I was under the impression that you should be able to tunnel layer 2 traffic which doesn't seem like it would work if your on different networks.

Also is it necessary to have IP's on the gre interfaces?

All the example setups I've found have IP's on them but I thought that the idea of the tunnel was similar to having a bridge connecting the two sides so an IP would be optional.

hi,

well, i'm not trying to teach you
why we need different subnet? in routing there is a mechanism called Split Horizon.
The routers get confuse when seeing 2 identical networks. it cant determine which way to pick the route prior forwarding the packet. so the router stops its function.
the same goes in tunneling - even in theory - your Q is correct.

and, the good thing is for monitoring - you know which traffic from and to

HTH.

Thanks, I finally got the gre tunnel working it doesn't do exactly what I'd hoped but it works