I have never used this device but after reading the manual
(which is here).
To configure it you can either use the install wizard which is windows only or after you have connected it all, you open a web browser and go to 192.168.2.1, from there you can configure it.
It will not replace your cable modem. But you do need one which has an ethernet port on it. Which you then connect to the WAN port on the device.
Please have a read of the manual before you buy it.
