Linux Networking Cookbook

3.2. Configuring Network Interface Cards on Debian

Problem

You have installed Debian Linux on your firewall box, so you're ready to configure your network interface cards.

Solution

In Debian, you'll edit /etc/network/interfaces and /etc/iftab. /etc/iftab is part of the ifrename package.

First, configure the LAN NIC with a static IP address appropriate for your private addressing scheme. Don't use DHCP to assign the LAN address. Configure the WAN interface with the account information given to you by your ISP. These examples show you how to set a static local IP address and a dynamic external address.

Do not connect the WAN interface yet.

In this example, eth0 is the LAN interface, and eth1 is the WAN interface:

	##/etc/network/interfaces

	# The loopback network interface
	auto lo
	iface lo inet loopback

	#lan interface
	auto eth0
	iface eth0 inet static
	     address 192.168.1.26
	     netmask 255.255.255.0
	     network 192.168.1.0
	     broadcast 192.168.1.255

	#wan interface
	auto eth1
	iface eth1 inet dhcp

If your WAN address is a static public routable IP address, configure the WAN interface using the information supplied by your ISP. This should include your ISP's gateway address, and your static IP address and netmask, like this:

	auto eth1
	iface eth1 inet static
	       address 1.2.3.4
	       netmask 255.255.255.0
	       gateway 1.2.3.55

Then, add your ISP's DNS servers to /etc/resolv.conf (don't do this for a DHCP WAN address):

	##/etc/resolv.conf
	nameserver 1.2.3.44
	nameserver 1.2.3.45

There is one more step just for Debian: nail down ...