Internet Connection Sharing in Ubuntu 11.04 using Firestarter

Unfortunately, my only option for internet access is to use a 3G modem. I need to share this connection with my Bluray player and, more importantly, my Xbox. Firestarter makes this easy to do.

Firestarter is a GUI firewall for Linux that can enable Internet Connection Sharing and has lots of nice features.

I am assuming the network interfaces are already set up and working in Ubuntu. Install Firestarter from the Ubuntu Software Center or from a terminal:

sudo apt-get install firestarter

Start Firestarter which will open a wizard. Click Forward at the Welcome screen. On the Network Device Setup screen, select the interface that connects to the internet. Mine is ppp0 since I'm using a 3G modem. Click Forward.

On the Internet Connection Sharing screen, enable sharing and select the interface connected to your internal network. Mine is wlan0 for my wireless connection. If you want Firestarter to act as a DHCP server for the local network, enable this feature. The default DHCP server settings should be OK. If you have a router on the local network, it is probably already acting as a DHCP server so you won't need to enable it in Firestarter. Click Forward.

On the last screen, click Save to save your settings and start the firewall.

Notes for Xbox Live:
You have to forward some ports that Xbox Live uses. Otherwise the Xbox network test will report a NAT type of Moderate (the goal is type Open). I never had any problems using Xbox Live with a Moderate NAT, but I wanted to set it to the recommendation of Open. Click the Policy tab and open ports 3074 and 88. There are other ports that Microsoft recommends to forward, but these two gave me Open status.