My Xbox doesn't want to find modem

I don't know how to do it but someone might want to put the modem in the modem forum and say that it doesn't work very well with the xbox

I'm signed in into my PC and don't have an Xbox console.

And: where can I find "Test Xbox Live connection"?

I don't have a router, I surf with an usb mobile modem; the error code you can find above in my first request.

I am signed in into my Xbox account, but the system doesn't download my data.

Hey

I can connect to my wireless network and i can connect with my router via ethernet. But the thing is that my router doesn't have a gigabit port so i get low download speeds. I want to connect my xbox directly with my modem in which my optical fiber is connected.
My modem/ONU connects to my router. I want to connect to my modem directly as it has a gigabit port. If i am using a computer i can connect directly to my modem via ethernet by usind Dial Up and entering my username and password. But Xbox doesnt have dial
up so i dont know what to do. Anyways thank you for taking your time to reply.

Also, I don't have a modem. It's like a small box on the wall that I plug my ethernet cable into. It isn't a standard modem. It doesn't run off of my house's power, it's hooked up to a box outside. I can find a picture, and show you what I'm working with,
if you'd like?

Type your router's IP into your browser, and try to find your XBOX's IP. Once found, delete it from the system, and plug in again. if this doesn't work, contact the modem/router manufacturer.