Can cable modem service provider detect my Network Computers

[robinson]

Can my cable service provider check my cable internet service? If I add a router and connects with other computer to my service, One thing that I initially installed the service on a single computer?
My Cable Operator told me that adding another computer would cost about $7 a month.
I don't need both computers online at the same time.

[denny]

The ISP can't tell how many machines in your network behind the router. You only obtaining a IP Address from your ISP, so its not a matter. They're likely charge you $7.0 for another IP address. If you get a router, using it, you can assign internal IP addresses to your network machines while only using one from your ISP.