Set up iptables NAT rules 1.2b2

Set up iptables NAT rules is an example IPTables 1.2.1 script for a multi-homed firewall.

Please feel free to send me any comments or suggestions.

Current versions and documentation are available at http://www.sentry.net/~obsid/IPTables/rc.scripts.dir/current/

Sample:

## Variables ##
IPTABLES="/usr/local/sbin/iptables" ## Default IPTables >= v. 1.2.0
#IPTABLES="/usr/local/bin/iptables" ## Default IPTables <= v. 1.1.2

LOOPBACK="lo" ## Loopback Interface
EXTERNAL="eth0" ## External Interface
INTERNAL="eth1" ## Internal Interface
DMZ_IF="eth2" ## DMZ Interface

INTERNAL_NET="192.168.1.0/24" ## Network address for the internal network
DMZ_NET="192.168.2.0/24" ## Network address for the DMZ

## INT_IP="192.168.1.10" ## IP Address of Internal Interface
INT_IP=`ifconfig $INTERNAL | grep inet | cut -d : -f 2 | cut -d -f 1`

## DMZ_IP="192.168.2.10" ## IP Address of DMZ Interface
DMZ_IP=`ifconfig $DMZ_IF | grep inet | cut -d : -f 2 | cut -d -f 1`

EXT_IP="216.162.197.10 ## IP Address(es) of External Interface
216.162.197.11" ## (This variable not used at this time).
## EXT_IP=`ifconfig $EXTERNAL | grep inet | cut -d : -f 2 | cut -d -f 1`

LOG_LEVEL="notice" ## Default log level: kern.notice

## Attempt to Flush All Rules in Filter Table
$IPTABLES -F

## Flush Built-in Rules
$IPTABLES -F INPUT
$IPTABLES -F OUTPUT
$IPTABLES -F FORWARD

## Flush Rules/Delete User Chains in Mangle Table, if any
$IPTABLES -F -t mangle
$IPTABLES -t mangle -X

## Delete all user-defined chains, reduces dumb warnings if you run
## this script more than once.
$IPTABLES -X

## Set Default Policies
$IPTABLES -P INPUT DROP ## Highly Recommended Default Policy
$IPTABLES -P OUTPUT DROP
$IPTABLES -P FORWARD ACCEPT