Each cable modem has its own unique identifier ("MAC Address"). The ISP sends the signal into your home and that signal looks for the "MAC Address" they have on record. After the ISP "handshakes" with your recognized modem, you now have access to their signal unfettered, therefore, you can connect ANY ROUTER you wish to the modem without having to tell your ISP that you even have a ROUTER. So, in short, you DON'T HAVE TO CALL ANYBODY if you bought your own ROUTER.
