Since Ubuntu 9.10 Karmic Koala, Ubuntu has an inbuilt way of sharing any connection. There are a couple usage scenarios for this:-
- You want to share your mobile broadband connection with other computers on the network
- You want to use your Ubuntu machine to extend your network wirelessly e.g. Your laptop is connected to the network via it’s wireless adapter, which is then connected to another machine via a CAT 5 or CAT 6 cable, enabling the other machine to connect to the network and internet.
I wouldn’t envisage using this to share a DSL broadband connection since most people will already be using an ISP supplied router to do this.
Using it is as simple as enabling the method “Shared to other computers” in the network connection in network manager.
This turns your machine into a mini DHCP/DNS server and starts handing out IP addresses in a 10.x.x.x address range. The machine then NAT/routes any traffic coming in on that interface and forwards it to the networks real gateway. I’ve used it a few times now and it works well.