You didn't describe your setup in any detail. I am assuming you have an ethernet connection for your LAN and either a second ethernet connection or some other way to connect to the Internet. In which case, all you should need to do is enable ip forwarding.
I am basing my info on Ubuntu 6.10 -- it is probably still the same. I don't know of a graphical way to do this. In /etc/sysctl.conf I find the following two lines:
# Uncomment the next line to enable packet forwarding for IPv4
# Uncomment the next line to enable packet forwarding for IPv6
As directed, uncomment one or both lines. (IPv4 is the Internet Protocol we have been using for eons. IPv6 is a newer version that is now seeing some use. With XP you probably only need worry about IPv4.) You can use your favorite text editor, but you need to be root
to edit this file. It is always a good idea to backup configuration files like this before you edit them. (That way, if some *bad* happens, you can always go back.)
This will allow packets from other computers on the LAN to get to the Internet. But those other computers must be configured to use the LAN. They can either be configured manually or with a DHCP server on the LAN. You can use your Ubuntu gateway as a DHCP server by installing the package dhcp3-server
. You should be able to find many resources in helping you configure it. For general information about DHCP, see the Wikipedia article
. In trying to find something more basic than the Wikipedia article, I found this FAQ
. I am not sure if it is simpler, but it might have some good links.