I need DOCSIS 3.0 , and my Motorola 6020 die after only a year of use -lrb- keep drop the connection -rrb- , so I `` upgrade '' to the 6121 . after be on the phone with Comcast for nearly a hour to get it up and run , it finally connect . 5 min after I hang up the phone with they it disconnect . it keep connect and disconnect randomly after that . the connection , when it do connect , do not hold on for long . I think I be do with Motorola modem . I have a much older one that work great , can not remember the model , unfortunately it be only DOCSIS 2.0 and I be pay for 3.0 service , something Motorola can not seem to get right .