[MovedGoalPosts]

I think you have been buying the wrong type of router. You have been buying a router with inbuilt modem intended for use with ADSL broadband. ADSL is supplied via a BT type phone line.

You have cable broadband which works on a completely different basis. ADSL routers will not work, you need a DSL/Cable router, such as the Linksys WRT54G series indicated above. That then connects to the ethernet port on the cable modem yuo already have.