provided by pank@pank.org & kelly@qkelly.com
範例
WAN IP 211.72.242.40 NETMASK 255.255.255.0
LAN IP 192.168.1.1 NETMASK 255.255.255.0
內部機器 192.168.1.246, gateway 任意, 也可以不設
port 2222 mapping 到 192.168.1.246:22
iptables -t nat -I PREROUTING -p tcp -d 211.72.242.40 –dport 2222 -j DNAT –to 192.168.1.246:22
iptables -t nat -I POSTROUTING -p tcp -d 192.168.1.246 –dport 22 -j SNAT –to 192.168.1.1