Open TCP Port Not Recognized By Router

Question

I have designed over a dozen boards that use the W5500 for TCP communications over a LAN. I recently tried to access the W5500 on a board which was configured in TCP mode and was in the Listen state. If I use a browser (like IE11) over the LAN, there is no problem connecting to port 80 of the W5500. However, if I set up my Netgear FV318 router for port forwarding to port 80 of the same W5500, the router does not recognize that the port is open!! I spent considerable time (and money) working with the tech support people at Netgear to verify that the problem was with the W5500 and not the router. I further confirmed this problem when I attempted to connect to the W5500 through the LAN using an ESP-8266 Wi-Fi device. The ESP-8266 successfully connects to an IP camera on the LAN but fails to connect to the W5500 on the same LAN. I would like to find someone who has anyone successfully used port forwarding with the W5500 as the target device.

Eugeny · Answer

As long as you were talking to support, you most probably have much more technical information about the incident. Can you share it please? Did you investigate packets and their flow?