@Musitg
What’s the modem type and model number? I don’t have a modem with the router included but if I know the modem brand and model number then maybe I can find the answer online. I personally don’t like gateways because a lot of the time the ISP won’t let you have access to the settings. I use the ISP’s modem only (it’s a newer model) and have my own router to adjust the settings to my preferences.
From another post about the same situation: