when you install this modem , if you be replace a Comcast rental , ensure you have the MAC -lrb- CMAC or HFC MAC -rrb- address handy , and call Comcast first & tell they you want to provision a new modem . after several hour of try to use they webpage that come up , I have to call . also , ensure you have the correct MAC address ; for example , a `` d '' can look like a zero -lrb- `` 0 '' -rrb- w\/those tiny letter , which be my only complaint on this modem so far . otherwise , the modem seem to be work great for I -lrb- though I do have to reset my wireless router and then reboot the modem to get the 2 to work together -rrb- . the modem work fine with my Ooma telo box to provide VOIP ... if you be use comcast-provided voip\/phone or will be , this modem will not work I think ; you need a telephony modem .