O meu script e este
#!/bin/bash
# (1) Policies (default)
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP
#Carrega módulos
modprobe ip_tables
modprobe iptables_nat
# (2) User-defined chain for ACCEPTed TCP packets
iptables -N okay
iptables -A okay -p TCP --syn -j ACCEPT
iptables -A okay -p TCP -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A okay -p TCP -j DROP
# (3) INPUT chain rules
# Rules for incoming packets from LAN
iptables -A INPUT -p ALL -i eth1 -s 192.163.1.0/8 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 127.0.0.1 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 192.163.1.3 -j ACCEPT
iptables -A INPUT -p ALL -i lo -s 10.0.0.1 -j ACCEPT
iptables -A INPUT -p ALL -i eth1 -d 192.163.1.255 -j ACCEPT
# Rules for incoming packets from the Internet
# Packets for established connections
iptables -A INPUT -p ALL -d 10.0.0.1 -m state --state ESTABLISHED,RELATED -j ACCEPT
# TCP rules
iptables -A INPUT -p TCP -i eth1 -s 0/0 --destination-port 21 -j okay
iptables -A INPUT -p TCP -i eth1 -s 0/0 --destination-port 22 -j okay
iptables -A INPUT -p TCP -i eth1 -s 0/0 --destination-port 80 -j okay
iptables -A INPUT -p TCP -i eth1 -s 0/0 --destination-port 113 -j okay
# UDP rules
iptables -A INPUT -p UDP -i eth1 -s 0/0 --destination-port 53 -j ACCEPT
iptables -A INPUT -p UDP -i eth1 -s 0/0 --destination-port 2074 -j ACCEPT
iptables -A INPUT -p UDP -i eth1 -s 0/0 --destination-port 4000 -j ACCEPT
# ICMP rules
iptables -A INPUT -p ICMP -i eth1 -s 0/0 --icmp-type 8 -j ACCEPT
iptables -A INPUT -p ICMP -i eth1 -s 0/0 --icmp-type 11 -j ACCEPT
# (4) FORWARD chain rules
# Accept the packets we want to forward
iptables -A FORWARD -i eth0 -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
# (5) OUTPUT chain rules
# Only output packets with local addresses (no spoofing)
iptables -A OUTPUT -p ALL -s 127.0.0.1 -j ACCEPT
iptables -A OUTPUT -p ALL -s 192.163.1.3 -j ACCEPT
iptables -A OUTPUT -p ALL -s 10.0.0.1 -j ACCEPT
# (6) POSTROUTING chain rules
iptables -t nat -F
modprobe iptable_nat
iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
iptables -t nat -A POSTROUTING -o eth1 -j SNAT --to-source 10.0.0.1
echo 1 > /proc/sys/net/ipv4/ip_forward
mais uma vez obrigado silvia