Every ISP has is own ?shtick?, some times different ones in different geographical locations
The following may apply:
Most DSL services use PPPOE for authentication, and in case of self install insist that you install first their software in order to obtain ID, and Password (authentication).
In such a case you first install the software including the PPPOE program (usually WinPOET), during the installation the Id and Password will appear on the screen (write them down). When every thing work well, and you have a solid Internet service. You can put on the Cable/DSL Router.
You log on to the Router, in the PPPOE menu type username and password. Make sure PPPOE is checked. Set the router to obtain IP automatically (unless you have a static account).
As long as you don't switch off the DSL Modem, and the Router you are connected "forever" (the computer can be switched off). If you switch them off, when you switch them on again, it will take a minute, and the Router will automatically connect to the DSL ISP.
You can uninstall WinPOET and whatever else, the ISP dished you.
The Router's PPPOE capacity is independent from the Computer, and it keeps the connection alive.