Farid Ahmadian / Scripts

Simple firewall example

Public domain


#!/bin/bash
# Internal interface = eth0
# External interface = eth1
# Localnet range = 192.168.0.0/24
# Flushing
iptables -t filter -F
iptables -t filter -X
iptables -t filter -Z
# Drop everything
iptables -t filter -P INPUT DROP
iptables -t filter -P OUTPUT DROP
iptables -t filter -P FORWARD DROP
# Accept local connections
iptables -t filter -A INPUT -i lo -j ACCEPT
iptables -t filter -A OUTPUT -o lo -j ACCEPT
# Accept dns connections
iptables -t filter -A FORWARD -i eth0 -s 192.168.0.0/24 -p udp --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -t filter -A FORWARD -i eth1 -d 192.168.0.0/24 -p udp --sport 53 -m state --state ESTABLISHED -j ACCEPT
# Accept http connections
iptables -t filter -A FORWARD -i eth0 -s 192.168.0.0/24 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -t filter -A FORWARD -i eth1 -d 192.168.0.0/24 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT
# ICMP transit
iptables -t filter -A FORWARD -i eth0 -d 192.9.9.3 -p icmp --icmp-type echo-request -j ACCEPT
iptables -t filter -A FORWARD -i eth1 -s 192.9.9.3 -p icmp --icmp-type echo-reply -j ACCEPT

BY: Pejman Moghadam
TAG: firewall, iptables, bash-script, bash
DATE: 2007-07-11 21:40:51


Farid Ahmadian / Scripts [ TXT ]

With many thanks and best wishes for dear Pejman Moghadam, someone who taught me alot in linux and life :)