After switching my modem from bridge to router, I tried to browse from external (Internet) connection on port 80 and got an unexpected login and password page to login on modem administrative web interface.
You could waste your life searching on modem web interface how to chance the port 80 (web administrative) to another port and you won’t get it. To do the black magic go to “Advanced Setup” -> “NAT” -> “Virtual Servers” and add the rule to use port 80, with this the modem tells you that the modem web interface will be change to port 8080.
But, what’s if you try to use a virtual server on port 8080? haha, you’ll get “duplicity error”, the port is in use.