Set up Ubuntu server as router

Question

I just installed Ubuntu 10.04 LTS server on a old desktop PC with a dual port network card I would like to use as router for my home network. How do I have to set up the interfaces so that the internet connection is passed through the server?

Answer 1

The first step when configuring Linux as a router is to enable IP forwarding:

$ echo "1" > /proc/sys/net/ipv4/ip_forward

Now the OS can route packets between interfaces.

Next use iptables and netfilter to create traffic rules.

I would suggest that you use a front-end to iptables and Netfilter in order to configure your router and manage the interface rules and policies.

If you prefer a GUI then see some of the other helpful answers on this page.

If you would like to hack at the command line and experience the true power of the Force, then try the excellent Shorewall front-end to iptables and netfilter which will allow you to easily configure your router straight away. Yet, as you learn more about routing Shorewall will allow increasingly fine-grained configurations and packet level network flow control.

The shorewall package is available in the Ubuntu repositories (choose either the shell or Perl package). The Shorewall site has great documentation and helpful tutorials for a multitude of scenarios. The basic 2- or 3- interface examples should get you going.

Answer 2

The easiest way would be to use iptables. Have a read on iptables over on the Ubuntu community site. You could also use something like firestarter for a nicer GUI experience.

Personally, I would recommend using a dedicated gateway distro such as ipcop, m0n0wall or an all-in-one system like ClearOS or Untangle. It would simplify the management of the firewall as well as offer you quite a few other features (also, with simplicity built in).