I'm looking for troubleshooting ideas. The setup is a cable modem connected to a Cisco RV180 router. There is a switch connected to one router port and two PLCs connected to the switch. Each PLC has an embedded web server. I can connect a laptop to the switch, or to a router port, and call up the webpage of either PLC. I've configured the router's firewall to allow traffic on port 80 and to forward it to one PLC. The puzzle is that PLC A (192.168.1.5) is accessible from outside the network, as expected, when 192.168.1.5 is entered in the NAT field in the firewall page of the router setup screen. But when I change it to 192.168.1.8, the IP of the other PLC, it's not accessible from outside the network. I can ping it from outside the network but it won't respond to requests from a browser. And, as I mentioned, it does respond to browser requests from within the network. It seems like it has to be something in the router but I can't think what to try. The page on the PLC that does work is much simpler and smaller than the page on the PLC that won't connect but I can't think how that would make a difference.