Comcast XFINITY → [Install] How to activate my newly purchased cable modem ?

I'll keep this simple, I just purchased a Motorola Retail Motorola Surfboard SB6141 DOCSIS 3.0 Cable Modem and I'd like to use it to replace the existing rented modem. Can I do this online or must I call the service desk for them to do it?

First, try connecting your computer DIRECTLY to the modem, and connecting it up to the cable. Let it sync up, and wait until it stays connected for a few minutes (it's normal for it to go into a firmware update or two the first time it connects.)

Open up a browser and try to go somewhere. If it works, it will take you to the walled garden where you can enter your information.

If that doesn't work, then call Comcast and tell them you want to provision a new modem. Before doing that, write down the serial number and HFC MAC (or RF MAC) address. That will be needed.

After the provision it, it may yet again reboot a few times until the firmware is updated (even if it was already updated) and other settings are completed.

Just plug it in and attempt to visit any website. You'll be redirected to the activation portal. Follow the prompts, then reboot the modem.

If that fails, just call 1-800-COMCAST.

»customer.comcast.com/hel ··· -devices

Introduction

You can activate your XFINITY services through a click of the mouse or by a simple phone call! Once you have set up and connected all your devices, you have two options for activating your services.

Activating Your Equipment Online
Activating Your Equipment Over the Phone

All SIKs include activation information. You can find this in your red XFINITY folder.

Activating Your Equipment Online

Go online to www.comcast.com/activate to be connected to the XFINITY Activation Web page.
For XFINITY Internet customers, you will automatically be connected to this page once you connect and power on your modem.
While on the XFINITY Activation Web page, verify your identity using your account number and your phone number.
You can locate your account number on your billing statement, on your Activation Card within your Self Installation Kit or within your email confirmation (if applicable).
Complete activation by following the activation screens.
For additional information review How to Install Your Self Installation Kit (SIK) Devices or visit »customer.comcast.com/hel ··· finstall.

Activating Your Equipment Over the Phone

Call 1-855-OK-BEGIN (1-855-652-3446).
While on the line for telephone activation, you will need:
The phone number associated with your account.
The last four digits of the equipment serial number(s).
The location of the equipment (living room, bedroom, etc.).

Did you buy it retail or off of ebay?

Thanks everyone, I'll give it a try a bit later (done! )

Retail, ebay is too risky in this case. I read too many horror stories about ebay or used and the problems the purchaser had.

Thank you everyone, I'm now using the new cable modem.

You did the right thing by buying retail and see? It worked perfectly.

Yup and it's still working

I'm very happy for all the advise and warning DSL Reports has provided.

Just hook it up and go to comcastsupport.com
it will activate automatically
takes 5-10 mins but you don't have to do anything.

When you return your Comcast supplied rental modem, make SURE you get a receipt. You will need to retain that receipt, along with the receipt for your customer owned purchased modem. Plan on keeping them someplace safe FOREVER. Comcast has been known to begin charging a rental fee for for your own person modem YEARS after and then require that you show proof that it's your modem.