I have a device on my private network which I don't wish to allow to directly access the internet from my gateway. Instead, I want to tunnel that traffic from my gateway to another server (also mine) and have the traffic appear to originate there. My gateway is a smoothwall firewall and the other server is a ubuntu server. I'm hoping there's a solution that will divert all traffic from a given MAC through the tunnel to the remote server... but any solution that will accomplish this is welcome.
This can be done at the IP layer rather than at layer 2.
You'll have to read up on iptables a little, some helpful links are below. Just keep in mind you're looking to get the traffic to the 2nd server, you can do that with NAT on your gateway if you want a plain and simple solution. On the 2nd server you'll need to NAT.
If an unencrypted and unauthenticated setup is sufficient, you can use IP in IP or GRE tunneling to tunnel the traffic between the gateway and the server. If you need more security use something like OpenVPN to setup a secure tunnel between the gateway and the server.
Once the tunnel is setup, configure the gateway to route traffic from the device over the tunnel.
I'm not sure if NAT or a PtP tunnel will do the trick (unless I'm simply not seeing something in those options which is readily apparent to you). I'm not simply trying to get traffic from the NATted device to the remote server, rather, I want the NATted device to use the remote server as it's gateway (vs using the local gateway). So, somehow, I need to get traffic for that one device routed to the remote server which will then gateway it to wherever it must go.
Secure would be nice, but is certainly not a requirement... IOW, I'd probably play with securing the connection to see if there was any performance degradation, but an unsecured connection is just fine at this juncture.