iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -o ppp0 -j MASQUERADE

iptables -A INPUT -p gre -j ACCEPT
iptables -A FORWARD -p gre -j ACCEPT

//=====================================================

#!/bin/sh

iptables="/sbin/iptables"
modprobe="/sbin/modprobe"
depmod="/sbin/depmod"

EXTIF="eth1"
INTIF="eth2"

load () {

    $depmod -a

    $modprobe ip_tables
    $modprobe ip_conntrack
    $modprobe ip_conntrack_ftp
    $modprobe ip_conntrack_irc
    $modprobe iptable_nat
    $modprobe ip_nat_ftp
    $modprobe ip_conntrack_pptp
    $modprobe ip_nat_pptp

echo "enable forwarding..."
echo "1" > /proc/sys/net/ipv4/ip_forward
echo "enable dynamic addr"
echo "1" > /proc/sys/net/ipv4/ip_dynaddr

#  start firewall

    #default policies
    $iptables -P INPUT DROP
    $iptables -F INPUT
    $iptables -P OUTPUT DROP
    $iptables -F OUTPUT
    $iptables -P FORWARD DROP
    $iptables -F FORWARD
    $iptables -t nat -F


echo "  opening loopback interface for socket based services."
$iptables -A INPUT -i lo -j ACCEPT
$iptables -A OUTPUT -o lo -j ACCEPT

echo "  allow all connections OUT and ONLY existing related ones IN"
$iptables -A INPUT -i $INTIF -j ACCEPT
$iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
$iptables -A OUTPUT -o $EXTIF -j ACCEPT
$iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
$iptables -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
$iptables -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
$iptables -A FORWARD -j LOG --log-level 7 --log-prefix "Dropped by firewall: "

$iptables -A INPUT -j LOG --log-level 7 --log-prefix "Dropped by firewall: "
$iptables -A OUTPUT -j LOG --log-level 7 --log-prefix "Dropped by firewall: "

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

$iptables -A INPUT -i $INTIF -j ACCEPT
$iptables -A OUTPUT -o $INTIF -j ACCEPT

echo "  Allowing packets with ICMP data (pings)"
$iptables -A INPUT -p icmp -j ACCEPT
$iptables -A OUTPUT -p icmp -j ACCEPT

$iptables -A INPUT -p udp -i $INTIF --dport 67 -m state --state NEW -j ACCEPT

echo "  port 137 for netBios"
$iptables -A INPUT -i $INTIF -p udp --dport 137 -j ACCEPT
$iptables -A OUTPUT -o $INTIF -p udp --dport 137 -j ACCEPT

echo "  opening port 53 for DNS queries"
$iptables -A INPUT -p udp -i $EXTIF --sport 53 -j ACCEPT

#echo "  opening port 22 for internal ssh"
$iptables -A INPUT -i $INTIF -p tcp --dport 22 -j ACCEPT


$iptables -A INPUT -p gre -j ACCEPT
$iptables -A FORWARD -p gre -j ACCEPT

echo "  opening port 1723 for VPN Server"
$iptables  -A INPUT -p tcp -i $EXTIF --dport 1723 -m state --state NEW -j ACCEPT

echo "  opening port 80 for webserver"
$iptables -A INPUT -p tcp -i $EXTIF --dport 80 -m state --state NEW -j ACCEPT

echo "  opening port 21 for FTP Server"
$iptables  -A INPUT -p tcp -i $EXTIF --dport 21 -m state --state NEW -j ACCEPT

echo "  opening ssh for web on port 2609 for firewig"
$iptables -A INPUT -p tcp --dport 2609 -j ACCEPT
$iptables -A OUTPUT -p tcp --dport 2609 -j ACCEPT

echo "  opening ssh for web on port 22  for betty"
$iptables -A PREROUTING -t nat -i $EXTIF -p tcp --dport 22 -j DNAT  --to 192.168.10.96:2302
$iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.10.96 --dport 2302 -j ACCEPT

#echo "   opening Apache webserver for HoH"
$iptables -A PREROUTING -t nat -i $EXTIF -p tcp --dport 80 -j DNAT --to 192.168.10.96:80
$iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.10.96 --dport 80 -j ACCEPT

}
flush() {
    echo "flushing rules...."
    $iptables -P FORWARD ACCEPT
    $iptables -F INPUT
    $iptables -P INPUT ACCEPT
}

case "$1" in

    start|restart)
    flush
    load
    ;;
    stop)
    flush
    ;;
*)
    echo "usage: start|stop|restart."
;;

esac
exit 0
}