N900 as main modem/router?

Can my router be used a direct modem/router? I wanna use it as my main instead of the free isp modem/router but whenever i plug the rj45 in the ethernet it doesn’t work

The N900 is a router, only. It must be connected to a modem’s output.

Oh okay. So how can i use my n900 as my second router because of my isp’s free modem/router is ■■■■■■. Do i need to configure it up? Or plug and play? Thank you very much

I replied to your other post.