Scenario:
Using DDwrt on a linksys router. I want to port forward a specific public IP address to internal IP 192.168.0.20 port 80 using IPtables. Not sure how to do this any help would be appreciated.
Something like:
iptables -t nat -A PREROUTING -d <public-ip> -i <wan-interface> -j DNAT --to 192.168.0.20
should work. If you want to forward only TCP port 80 on the public IP, you can do:
iptables -t nat -A PREROUTING -p tcp --dport 80 -d <public-ip> -i <wan-interface> -j DNAT --to 192.168.0.20:80
iptables -t nat -A PREROUTING -d <public-ip> -d <wan-interface> -p tcp --dport 80 -j DNAT --to-destination 192.168.0.20
to specify only port 80 traffic, otherwise that 192.168.0.20 will become the recipient of all traffic to the public IP.