IP Masquerading

This is a very simplified diagram showing the sample network layout for IP Masquerading. IP Masquerading is how one internet connection can be shared by many machines.
On Windows, this is called Internet Connection Sharing (ICS).
For this presentation, I'll be assuming that your Firewall/Gateway machine has two Ethernet controllers, and that eth0 is the external facing interface, while eth1 connects to the internal private network.

This is a very simplified diagram showing the sample network layout for IP Masquerading. IP Masquerading is how one internet connection can be shared by many machines.