Though I haven't done it yet, I am looking to upgrade my current modem, which I've had for years. Before I do, I'd like to have a run down of the procedure for setting the new modem up. I know it involves calling up Comcast, but haven't seen a clear procedure or anything spelled out.
There gonna send you the new one in the mail it will come with a brochure, Ethernet cable, 2 coaxial cables and a splitter and a power cable, to set it up it is pretty straight forward. Connect the modem to cable connection out of the wall, plug power cable in connect and Ethernet cable to PC or router. Then try to connect to internet will take you to xfinity page with me it did not so I had to call them up and you give the Mac address from the paper they send you or of your new modem and that's about it. Make sure you have your account info handy it will be on the paper they provide with your Mac address. Good Luck.
Basically the same thing. You will just give them the Mac adress or S/N off the modem. If you do decide to buy one go with the Motorola Sb6120 off of amazon littly pricey but I've heard of no problems with it like with Ubee one.
You simply swap cables to the new modem, call Comcast and tell them you want to register a new cable modem for your HSI account. They will take care of the reset. Takes just a few minutes. Just make sure the model you buy is listed on the approved modem list. I would only purchase a DOCSIS3 model these days, not the older DOCSIS 2 models. I own and use a Motorola SB6120 here, works great.
If the old modem is a rental, make sure you get it back to Comcast and get a receipt. They have been known to come back to you later and ask for payment for a returned modem. Always a good idea to cover your behind.
All this assumes the existing modem is a regular cable modem and not an EMTA used with Xfinity Voice service. If it is an EMTA (ie it has phone jacks), then your options are much more limited. There is only one choice, some Best Buy stores have a Comcast kiosk where you can buy an Arris TM722G, but you still need to schedule a tech visit to get it installed.