the install be easy . plug it in and call Comcast . they ask for the model # and MAC ID # . Comcast confirm that the sb6121 be a good choice . both number be easy to find , albeit print in very small print - have a magnifying glass ready . Motorola have a sticker on the side of the modem with the MAC ID , and several sticker in the box with the same info - to place on the computer around you home , I guess - in case you ever have to call you internet provider . I spend about 15 minute on hold with Comcast to get to a real person . they tech rep be very pleasant and helpful . she walk I through the step . basically , all I have to do be turn off my router . my computer , a 2011 Apple iMac , be plug into a wireless router , that be in turn plug into the new modem . Comcast find my modem and activate it . I do not even have to unplug from the router and connect directly modem to computer . once I get to a person at Comcast , it take about 10 minute . they tell I be to drop off the old modem so the rental could be take off my bill . speed test prior to swap modem average 10 to 15 mbp for download . after install the sb 6121 , download speed improve to 35 mbp . upload now come in at about 5.5 mbp . some user mention the sb6121 modem get warm . after a hour or so of download video , I find it be only warm to the touch - not hot . should have do this a long time ago . even if this new router fail some day , I now know it be no big deal to replace it .