Hello, friend!
I don't quite understand what you mean by opening the port. (Maybe it's you want to change the Layer 2 and Layer 3 working modes of the HG8145V5 LAN port.)
According to your problem description, the networking is as follows: HG8145V5 - Archer A6 - PC. You only need to connect the device through a network cable. The 192.168. 1.100 displayed on the ONT is the WAN IP address that the ONT sends to the Archer A6. 192.168.0.179 is a LAN IP address assigned by the router to the PC, which is fine. If the PC accesses the Internet, the IP address conversion process is as follows: 192.168.0.179-->192.168.1.100-->HG8145V5 WAN IP-->Internet.
If the problem is that Archer A6 fails to access the network after connecting to the port of the HG8145V5, the physical port of the HG8145V5 may not be bound to the WAN configuration. In this case, you need to log in to the WebUI of the ONT. Note that the administrator account and password of the device are used to log in to the WebUI of the device, and then bind the HG8145v5 LAN port connected to the Archer A6 in the WAN configuration.
Thanks!