table nat

-P PREROUTING ACCEPT
-P INPUT ACCEPT
-P OUTPUT ACCEPT
-P POSTROUTING ACCEPT
.........
-A PREROUTING -i wan -p tcp -m tcp --dport 88 -j DNAT --to-destination 192.168.1.100:88
-A PREROUTING -i wan -p udp -m udp --dport 88 -j DNAT --to-destination 192.168.1.100:88
-A PREROUTING -i wan -p tcp -m tcp --dport 80 -j DNAT --to-destination 192.168.1.200:80
.........
-A POSTROUTING -o wan -j MASQUERADE