Using Linux iptables or ipchains to set up an internet gateway / firewall / routerfor home or office.

This is a nice tutorial on using Iptables. It has a number of "cookbook" solutions to common configuration scenarios: Using Linux iptables or ipchains to set up an internet gateway / firewall / routerfor home or office

This tutorial will cover using a linux computer as a gateway between a private network and the internet. Any internet connection whether it be a dial-up PPP, DSL, cable modem or a T1 line can be used. In the case of most dial-up PPP connections and cable modem connections, only a single IP address is issued allowing only one computer to connect to the internet at a time. Using Linux and iptables / ipchains one can configure a gateway which will allow all computers on a private network to connect to the internet via the gateway and one external IP address, using a technology called "Network Address Translation" (NAT) or masquerading and private subnets. Iptables/ipchains can also be configured so that the Linux computer acts as a firewall, providing protection to the internal network.