Создание простейшего шлюза

Создание простейшего шлюза

#!/bin/sh

IPTABLES=/sbin/iptables
# EXTIF - external interface connected to the Internet
# INTIF - internal interface
EXTIF="ppp0"
INTIF="eth0"

echo "   External Interface:  $EXTIF"
echo "   Internal Interface:  $INTIF"

echo "   Enabling forwarding.."
echo "1" > /proc/sys/net/ipv4/ip_forward

echo "   Clearing any existing rules and setting default policy.."
$IPTABLES -P INPUT ACCEPT
$IPTABLES -F INPUT
$IPTABLES -P OUTPUT ACCEPT
$IPTABLES -F OUTPUT
$IPTABLES -P FORWARD DROP
$IPTABLES -F FORWARD
$IPTABLES -t nat -F
$IPTABLES -F
$IPTABLES -X

echo "   FWD: Allow all connections OUT and only existing and related ones IN"
$IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT

echo "   Enabling SNAT (MASQUERADE) functionality on $EXTIF"
$IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE