I have 8 computers, a switch and a modem. They all run windows 7 and connected to a windows 7 server. I replaced the clients with Ubuntu 12.04.3 and uninstalled the proxy from the windows 7 server and now I can connect to the internet on all clients. The issue is that I want to replace the Windows 7 server with Ubuntu 12.04.3 but I don't know how to configure it so that it can connect to the internet and share it.
What you are describing is using your Windows 7 server machine as a Masq/NAT router, and probably as a firewall as well. I have found the
Shorewall package to be an excellent, and user friendly package to assist in this task. This howto guide should get you pointed in the right direction:
If you have any more questions or troubles, I know quite a bit about
Shorewall, and would be willing to help.