WAN=eth0
LAN=ppp+
INT_NET=192.168.100.0/24
iptables -F FORWARD -v
iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT -v
iptables -A FORWARD -m conntrack --ctstate NEW -i $LAN -j ACCEPT -v
iptables -A FORWARD -m conntrack --ctstate DNAT -j ACCEPT -v
iptables -P FORWARD DROP -v
iptables -t nat -F POSTROUTING -v
iptables -t nat -A POSTROUTING -s $INT_NET -o $WAN -j MASQUERADE -v