Activating a New Cable Modem with Comcast

Do you get your Internet service from Comcast? If so, do you know if you’re renting your cable modem or own it out-right? If a Comcast tech set it up then there’s a good chance that you’re paying a monthly rental fee of about $10. If this is the case, you might want to buy your own cable modem and return the one you are renting. A new cable modem costs between $60-$130 depending upon which model you buy. You recover the cost of this new modem in 9-18 months through eliminating the rental fee.

Here are instructions on how to set up and register a new cable modem. These instructions are also helpful if you’re replacing a cable modem which has stopped working.

  1. Disconnect your current cable modem. Specifically, unplug the ethernet cable that connects it to your router or Macintosh computer. Also, unplug the coax cable that connects it to the wall jack and finally, disconnect its power cord.
  2. Plug in your new cable modem. Specifically, plug in the coax cable coming from the wall, then run the ethernet cable from the cable modem directly to your Mac (even if you have a router). Lastly, plug in its power cord. The cable modem will start up and try to connect to Comcast, but it won’t be able to do so since it’s not yet registered with Comcast.
  3. Call Comcast Tech Support. Their phone number should be on a recent invoice. Have a copy of your invoice handy because you’ll likely be prompted for either your Comcast account number or the phone number associated with your account. Once you get a person on the line, tell him or her that you’re setting up a new cable modem and you’d like him or her to guide you through it. The tech will ask you to read the MAC address which is printed on a sticker on the cable modem. The tech might also want the make and model of cable modem. Note: A MAC address has nothing to do with Macintosh computers. MAC stands for Media Access Control and is a unique identifying number.

The tech will then register the cable modem on their end and soon more and more lights on the cable modem will come on. This is a good thing, it’s progress. Soon your laptop will be connected to the Internet. Yay, things are working!

Note: I’ve had you bypass your router temporarily because Comcast won’t support the configuring of routers. They only support cable modems and 1 computer.  Now that you have your new cable modem working, you can hang up with Comcast and do the following.

  • Unplug the power cord from the Comcast cable modem. This is very important: make sure that all lights on the cable modem are off. If they aren’t off then your cable modem also provides your home with phone service. If this is the case then your cable modem has a battery in it and you’ll have to find the door and open it to pop out the battery. Once you have all of the lights off, then you’re good. Now proceed to the next step.
  • Move the ethernet cable from your laptop back to your router.
  • Re-insert the battery and power cord into the cable modem. The cable modem will start up, then it will see the router and pair with it. This is very important to understand. The cable modem can only pair with one device at a time. When it pairs it then permits that device to connect to the Internet. When the cable modem is off (i.e. has no lights lit up), it forgets the device that it last paired with and it’s ready to pair with a new device on start up.
  • Wait about two minutes for the cable modem to startup and all of its lights to turn on.
  • Make sure your laptop is connected to your router either wirelessly or using an ethernet cable. Open Safari and you should be able to view web sites. Yay, you’re done!

If you have problems getting all of this to work then you can go back to having your laptop plugged directly into the cable modem. However, to get this to work you’ll need to turn off the cable modem so it forgets its pairing with the router and will thus be ready to pair with your laptop when you connect your laptop using the ethernet cable to the cable modem.


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