Make your CentOS 4 box acting as an Internet Gateway/Router using IP Masquerading

P Masquerade is a form of Network Address Translation or NAT which NAT allows internally connected computers that do not have one or more registered Internet IP addresses to communicate to the Internet via the Linux server's Internet IP address.

The software interface which enables one to configure the kernel for IP masquerading is iptables.

To configure IP Masquerading, you need to have two LAN cards, a PC with CentOS 4 Linux installed.

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Home Gateway Firewall With DHCP Server For Connection Sharing

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.

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How To Masquerade On Linux (Internet Connection Sharing)

It's very simple to masquerade (internet connection sharing in Windows language ) on Linux with a few lines of iptables and ip_forward commands.

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