How to install a new modem-router to replace an old one?

Connect it to the coax line and power it up. Let it fully sync up with the system, and check that the front / top panel indicator light(s) are steadily lit. 

Then connect a computer to it and open up a browser. You *may* see their *Walled Garden* modem self registration page. If so, follow the screen prompts. Have your mobile telephone number, your Xfinity username and password, or the account number and telephone number associated with your Comcast account handy.

If not, try calling 1-855-652-3446. That is their device activation line.

If that doesn't work for you, you can call 1-800-comcast and tell a rep that you would like to have a new modem provisioned for service. Have the RF / CM / HFC MAC address and the serial number of it handy when you call.

Thank you for a very detailed description. Much appreciated.

@user_66909e Hello and thank you for reaching out over our Xfinity Community Forum. I see that the incredible @EG so graciously offered his expert assistance already, and we greatly appreciate him for that, and for his consistently expert and helpful advice on our Xfinity Community Forum. Please let us know if you have any issues installing your new gateway, or need any other assistance at all. We are here 24/7 and always more than happy to help in any way we can! I hope you both have an incredible day!

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