There's a server (node A), acting as the end point of a GRE tunnel. Also there is an Ubuntu server (node B, it sees Internet) acting as the termination point for the GRE tunnel. Some devices (nodes C1,2,3..) are connected to the server A and they see the server B, but not the rest of the internet, even DNS lookup doesn't work.
What do I have to configure on the server B to forward/route the traffic from and to devices C to the Internet. Ideally I'd also like to allow access to some addresses only. The question doesn't concern so much the topology, that bit seems pretty straight forward; the thing is that I'm just sort of lost in the tools like iptables/squid/route/etc, techniques like forwarding/routing/bridgin/etc and abbreviations OMG/why/are/there/so/many/abbreviations!
EDIT Server network configuration:
- Server A has an external IP 94.x.x.x (I really don't know anything else about it)
- A and B are connected through a GRE tunnel
- Server B has two network devices:
- eth0 with address 72.y.y.y (this is the Internet interface)
- tun0 with address 10.0.2.1 (this is the GRE tunnel interface)
- Terminals C# have IP's in the range 10.19.0.0/16
So the question is to forward the traffic from the subnet 10.0.2.1 to the Internet and vice versa (if the original IP of the request didn't change it would be perfect).