if you be have problem with set-up skip to paragraph five . have Comcast internet and telephone service -lrb- no tv -rrb- . order the Motorola sb6121 to replace the Comcast modem and save $ 7 per month and a few day later order the Oomo Telo box from Amazon to replace the Comcast telephone service and save another bundle . start by call Comcast to give they the information they need to activate the modem . the tech then tell I that I have to have the Comcast modem to have Comcast phone service . for I that be no problem as I just have to wait until my exist phone number be switch over -lrb- `` port '' -rrb- to the new service -lrb- one to two week -rrb- before install the sb6121 modem . Fine . two week later : ok , now to install the modem . while some reviewer seem to sail through a plug and play type process in a mater of minute and come up smile , many seem to run into real problem . I unfortunately end up with the later . some just apparently throw up they hand and return the modem to sender . do not do it . I stay with it . hopefully my experience will put you over with the come up smile guy . it literally take I all day . while Comcast 800 line people be patient and try , they be of little help . number one , I talk to three different tech ... that be after wade through the phone tree three time and wait on hold up to 20 minute each time . and two trip to the local Comcast office . each of course come from they own perspective and none know what the other have say . none of course could slide into my chair and hand on see-and-solve . throw in Comcast 's confusing terminology , and the seemingly unnecessary activation screen the company deem necessary for `` activate '' the modem and ... after five hour and the last tech , who tell I he screen show the modem be activate , I decide that if I be ever go to get the modem to work , I would have to figure it out for myself . then I do what I probably should have do in the first place . I haul the spaghetti pile of cable and hardware out of the cabinet , and disconnect everything right to the cable entrance at the wall . then I hook up the sb6121 modem to the cable , run the ethernet cable from the modem directly to a desktop computer -lrb- bypass the router ! -rrb- , plug in the computer , start the computer , and try to go online . it work ! the modem be activate , and it work ! so then I start over , connect first the modem , then the router , then the computer , plug in each , one at a time , modem-router-computer , only later add the Oomo Telo box and 2nd computer to the router when I know everything be work and work well . the Motorola sb6121 modem work like a charm . you 'll love it . ... we will not talk about the cable company -lrb- : Motorola could have help immensely by include in its instruction sheet the most basic of trouble-shooting information . could save some buyer 's hour ... and Motorola a lot of unnecessary return . for that , only four star .