How to use your own modem with Comcast

Typical frog in a hot pot scenario; when I joined Comcast the modem lease was like $1.50 a month, and I didn’t even think about it. As of recently it’s now crept up to $7.00 a month, which kind of made me sit up in shock. How much do those things actually cost, anyway?

Answer: $16 on eBay!

Ditching the leased Comcast cable modem in favor of your own is a surprisingly simple process. In my experience, Comcast won’t even try to (intentionally) stonewall your request or tell you it can’t be done in order to keep the revenue. Unfortunately, their techs are not exactly the brightest lights in the harbor, so you might have to train them a little on how to do it. Here’s how…

Step 1: Buy the modem
Go to your favorite new or used equipment source and buy the modem. Make sure your purchase includes any necessary power cord (wall wart); if not, buy that too. Theoretically, any DOCSIS 2 or later modem will work with most cable Internet packages, but to be sure, check this list for modems tested and approved by Comcast for compatibility. Extremely fast or fancy internet packages might have special requirements. Personally, I just searched eBay for the exact model # of my existing leased modem, and bought that one. My total cost was about $21 for the modem and a 12V wall adapter.

Step 2: Plug in the modem
Before you go connecting anything, turn the new modem over and copy down the “HFC MAC” number printed on the bottom to someplace more convenient. Note, there may be several different numbers printed on the modem; the “HFC MAC” is what you want. Technically the “number” is in hexadecimal, so it can also include the letters A-F. Double- and triple-check that you copied it correctly!

Disconnect your leased modem and plug the new one in its place. Verify that the lights come on and blink just as with your old one. (It will still ‘see’ a modem signal when connected, even if it’s not activated yet.) Once it’s lighting and blinking, power-cycle your wireless router (or whatever attaches to the modem Ethernet cable) to make sure it picks up a fresh IP address from the new modem. Just to be safe, reboot your computer(s) after this to make sure the newly rebooted router gives them a fresh address too. Now your modem, wireless router and computer will be “connected” to one another as far as your home network is concerned, although they won’t be able to reach the Internet through the new modem yet.

Step 3: Activate the modem
The one and only piece of information you (and Comcast) will need for this is the “HFC MAC” number you wrote down earlier. Call the Customer Service # on your Comcast bill, and say to them:
“Hi, I’d like to use my own modem and return my leased modem.” When I did this, the main customer service gave me a separate phone # dedicated to handling this request. Call that # and repeat the request.

The Comcast person on the phone will ask for the number from your modem. Not all of them are smart or well-trained, so they may not know which number, nor tell you the correct number to provide. Whatever they say (or don’t), give the “HFC MAC” you copied earlier. Now, this is important! Have the Comcast person input the number and then recite the number back to you, to make SURE they input it correctly. This is important!

Before you hang up, start accessing Web sites and see if they start working. If the Comcast person input the # correctly, your Internet should start working again almost immediately. If not, login to your wireless router’s status page (consult its manual for how to do this) and make sure it obtained an IP address, gateway IP and DNS servers from the modem. This information may be listed under a section titled “DHCP” (a protocol for devices to request and assign IP addresses.) Try powercycling the router again while the modem is activated to make sure it gets an address.

Step 4: Return the old modem
Hopefully, everything is working now! The last thing to do is to pack up the old modem and its wall plug in a box and return it to Comcast. If it came in an official Comcast box (e.g. “self-install kit”) and you still have that box, use that box – but if not, my experience is they aren’t that picky (I used a shoe box). There is a brick-and-mortar Comcast service/payment center by my house, so I just returned it in person. If this is not an option, ask the Comcast person how to return it by mail. My experience at the Comcast payment center was very positive – just handed the modem over, they scanned a barcode on the bottom and it was automatically credited to my account. They handed back a receipt with my name/account # and the modem details on it and I was on my way. My next bill had a partial refund for the part of the month I was no longer leasing the modem. Done and done!

If all does not go well…

If your new modem isn’t delivering the Internet goods after activation, the Comcast person (billing department) will transfer you to a separate department (tech support), who have the power to ‘ping’ your modem and make sure it is visible on their end. ‘Your’ modem in this case is defined as the modem matching the HFC MAC # linked to your account, which is why it’s very important that the billing person has input the correct #, and input it correctly, BEFORE this point. Otherwise they can ‘ping’ all day and not get any result because their system is looking for the wrong damn modem! The Tech Support person has the power to ping but NOT the power to add or correct MAC #s on your account, so this sucks. Likewise, the billing department has the power to enter MAC #s, but NOT to ping the modem! If this magic number entry gets cocked up somehow, it will take a 3-way conference call between you, tech support and billing to sort it out, and not all Comcastic techs know how to pull this off with all those complicated phone buttons. I spent two hours bouncing between departments because the barely-English-speaking billing person miskeyed the # the first time.

For the insanely bored or curious…

“MAC” number stands for Medium Access Control number, which is a globally unique number (burned into the device by the manufacturer) that identifies YOUR device among the millions of others out there just like it. The “medium” referred to is the physical cable. Since your block’s local cable segment is a shared resource, this number is necessary to identify you as a paying customer and route the right bits to and from YOUR specific modem. The difference between the separate “HFC” and “CPE” MAC #s is that the HFC number (I’m told this stands for “Hybrid Fiber-Coax”, i.e. residential cable networks) is the one that’s visible on the coax (cable) side of the modem that your ISP sees, and the other (“Customer-Provided Equipment”) is the Ethernet-side number that’s visible to your equipment (e.g. wireless router). Don’t tell Comcast that number by mistake; they can’t see it on the cable end.

3 Responses to “How to use your own modem with Comcast”

  1. Jacob says:

    Hi,

    My ISP says they cannot activate my modem. It was used with a different provider, but it is compatible with the new ISP (as per their list and tech support). What do you do if they can’t activate it, but did record the correct MAC? I’ve never heard of a modem have a once-and-for-all ISP burned into its Read-Only memory. Are they just trying to get me to get a leased modem?

  2. Sankar Srinivasan says:

    Thanks a lot for your help. It was very useful.

    Just one small feedback, in addition to MAC ID, the comcast tech support was asking for Customer S/N, which was there in the modem.

  3. James a says:

    If the previous provider will not “release” the modem from their pool of mac adresses, then you cannot take it to a different providr. This is even true across comcast branches, for example between california and georgia…

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