IPTABLES Allow LAN to WAN

IPTABLES Allow LAN to WAN

iptables is a command line utility for configuring Linux kernel firewall implemented within the Netfilter project.

We configure on Linux Server (iptables) to allow network 5.5.5.0/24 go to INTERNET. 

Here is our script:

#!/bin/sh

WAN="eth1"

LAN="eth2"

# ----- Enable Route ----- #

echo 1 > /proc/sys/net/ipv4/ip_forward

# ----- Default to drop packets ----- #

iptables -F

iptables -t nat -F

iptables -t mangle -F

iptables -X

iptables -P INPUT DROP

iptables -P OUTPUT DROP

iptables -P FORWARD DROP

# ----- Allow all local loopback traffic ----- #

iptables -A INPUT -i lo -j ACCEPT

iptables -A OUTPUT -o lo -j ACCEPT

# ----- Allow LAN SSH TO FIREWALL PORT 22 ----- #

iptables -A INPUT -i $LAN -p tcp --dport 22 -j ACCEPT

iptables -A OUTPUT -o $LAN -p tcp --sport 22 -j ACCEPT

# ---- Allow LAN Ping TO FIREWALL ----- #

iptables -A INPUT -i $LAN -p icmp  -j ACCEPT

iptables -A OUTPUT -o $LAN -p icmp -j ACCEPT

# ----- Allow LAN access Internet ----- #

iptables -A FORWARD -o $LAN -m state --state ESTABLISHED,RELATED -j ACCEPT

# ----- NAT and MASQUERADE -----#

iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT

iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE

# ----- EOF ----- #

Check on the client ip and test to INTERNET.

Finished,

#LINUX #IPTABLES #vannakk