Author: Cameron Camp <howto [at] logicalwebhost [dot] com>
If you’re trying to set up a home network, you probably want to set up a permiter facing computer connected to your DSL/Cable modem, and then put all of your computers behind that firewall box to keep them safe. This tutorial will show you how to use a single external connection on the gateway computer (using Iptables firewall), and a second internal connection on the same box so you can connect the computers on the inside of your home/office to it, and automatically give them IP’s when you hook them up (using DHCP server). Iptables can be very complicated, we will only configure a basic firewall, you can add more security later without breaking things. In Linux there are many ways to do this, this one is hopefully simple enough and will teach you the basics. I did this on a CentOS 5 box, though it would work on Debian variants with only slight modifications. During this tutorial I’m logged in as root, which you should generally NOT do, but it makes the tutorial simpler, but if you prefer to do it more securely, add “sudo” before each command and it will work.