partial iptables script

# Always accept loopback traffic
$IPTABLES -A INPUT -i lo -j ACCEPT

# Allow established connections
$IPTABLES -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# fowarding
$IPTABLES -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT
# Allow outgoing connections from the LAN side.
$IPTABLES -A FORWARD -i eth1 -o eth0 -j ACCEPT

# Masquerade.
$IPTABLES -t nat -A POSTROUTING -o eth0 -j MASQUERADE

# Enable routing.
echo 1 > /proc/sys/net/ipv4/ip_forward