How to install two cable modems with Comcast Internet

I recently rented an apartment that is part of a larger house. My landlords have Comcast high speed Internet service. The cable in my apartment is an extension of their cable wiring. They didn’t want to share their wireless network, so I needed to install my own cable modem.

Is a second cable modem without independent cabling from Comcast possible? A quick web search revealed mixed opinions that struck me as unreliable. And of course, Comcast’s own support site had nothing useful to say about it. So I just had to dive in and give it a try!

The short version

  1. Get a cable modem. You can lease one at a Comcast store and set up your account at the same time, but that’s not what I did. I bought a Motorola SB6120. It implements DOCSIS 3.0 and is compatible with Comcast. You can use any cable modem on the compatibility list.
  2. Connect the cable modem and let it sync until you get steady Power, Receive, Send, and Online lights.
  3. Write down the MAC ID found on the bottom of the cable modem.
  4. Call Comcast customer service at 1-800-266-2278 and set up a new Internet-only account. I got a special rate for the first year.
  5. Customer service will transfer you to tech support. Read them the MAC ID. They will provision the modem while you wait.
  6. You are now online!

A twisty maze of passages, all alike

Here’s the full story of how I developed this procedure through a series of discoveries and false starts. There’s a lot more explanation than the short version. I describe what I learned from each dead end. The only steps you need to follow are in the short version above.

You have the choice of supplying your own cable modem or renting theirs. You can pick one up at a Comcast store and set up your account at the same time. I elected to buy my own, which enabled me to do everything over the phone. Comcast has a list of cable modems they have certified as compatible with their system. I chose the Motorola SB6120 based on its easy availability at Best Buy and its solid reviews there and at Amazon.

The first thing I tried was connecting the cable modem and starting a browser. After waiting a few minutes until the Power, Receive, Send, and Online lights were on and no longer flashing, I opened my browser and got a Comcast activation page. I entered my landlord’s account number. It then told me to download and run the Comcast Installer Wizard. It dragged me through a long process, only to tell me, “An existing High-Speed Internet cable modem has been detected on your account.”

I took the choice, “I am adding an additional cable modem.” It then dumped me out with, “In order to add an additional cable modem to your Comcast account, please call 1-800-COMCAST for assistance.” This message doesn’t mean what it says, though, because when you call, you will find out that you can’t add a second cable modem to the account. You have to open a new account.

I called 1-800-266-2278 and got customer service on the line. (I started with tech support, based on the misleading message above, but they eventually transferred me to customer service.) The person I talked to did not understand the second cable modem issue very well. Just tell them you are adding a second cable modem and need to open your own account.

At first, they tried to foist a $50 “activation fee” on me. Don’t fall for it. Tell them you have your own cable modem and don’t need any help installing it. It’s all synced up and ready for them to bless it. That reduced my “activation fee” to $2. Whatever. I got a special discounted rate for the first year of service, month-to-month with no contract.

The customer service representative will give you your new Comcast account number. Be sure to write it down, because you’ll need it if you require help later.

Next, you get punted to tech support to provision or “activate” your service. They will ask for your cable modem’s MAC ID. You will find it on a sticker on the bottom of the cable modem. With that, and your account number, they will reach out and program your cable modem remotely. This takes a few minutes and restarts the modem. After that, you should be ready to go. Try pulling up a web page to test the connection.

If you arrived here after trying the Comcast Installer Wizard, you may find (like I did) that it left behind HTTP proxy settings in your browser that will now prevent it from working. (Thanks, guys!) If your browser no longer works, look through your browser settings for a proxy server with “comcast” in the name and delete it.

After fixing my browser, the connection worked perfectly. If I had been able to find out what I’ve written here before I started, the whole process would have taken less than half an hour.

Why is this fair?

Why is Comcast charging you for a whole extra account at the same location? I can’t speak for Comcast, but I may be able to shed some light on this. Cable Internet differs from DSL (telephone) Internet service in that all customers in a neighborhood share a common cable. As far as Comcast is concerned, you are a separate customer needing your own account, even though you might be located in the same house as another customer. After all, you’ll be using a certain chunk of bandwidth like every other customer.

Continue the conversation

I hope this article shed some light on how Comcast handles two cable modems in the same house. It is based on my own experience in California as of May 2011. If you had a different experience, I’d love to hear about it in the comments, so everyone can benefit.

36 thoughts on “How to install two cable modems with Comcast Internet

  1. Thanks for sharing the info … it helped me a lot. But I have a total different situation !!

    Comcast refused to open another account for me. It said that I can’t have two different accounts under the same line and can’t have a discount.

    I’m gonna call them again and speak with another support who can resolve this issue.

  2. In some areas (san mateo) Astound has a 50 mb cable modem deal. guaranteed price for two years, 40$ per month. They are calling it a “true” 50 claiming that is not a burst speed.

  3. If you live in your own home, have Comcast cable net, and have two internet-ready jacks in your house, can you set up modems on both jacks? I’m not going to pay for 2 accounts as the only user. I just want two modems so I can have all my devices on both ends hard-lined. I don’t wanna run cables all throughout my house from my one central router.

    • you can go to your local computer supply store and pick up (I’m not sure what they call them) basically you plug one into an electric plug behind your router using an ethernet cable and the other on plugs into another electric plug in another part of the house and then plug that into your device.

      1 service but connection where ever you want it

      • This only works if the two outlets are on the same breaker…. most outlets on opposite sides of the house are not.

    • The issue with using two modems is how cable Internet providers differentiate individual accounts. They use the MAC address (which is a theoretically unique number)to keep track of your account. The best thing I can recommend is to use a wireless access point and set up a wireless network. If you have devices that require hard connections then you will need to use a bridge (also called a game adapter). I run my office this way so that I don’t have to buy wireless adapters for my office equipment.

      • This may work for some devices, but not for CCDTV cams. :( I need a dedicated modem/hard wired. It does not grant browser access to my DVR if connected through a bridge. :(

  4. @JackInTheLinuxBox, Comcast says no. What you are describing is the situation I found myself in a year ago. I would call them up and ask anyway, in case they changed their policy. It wouldn’t hurt to call twice if you don’t get the answer you want the first time–I got somewhat different information from different people when I called.

  5. might it be easier and in the long run cheaper to purchase a higher powered router to reach the 2nd location

  6. Thanks for posting this, Todd. My situation is almost identical to yours. Funny thing is my modem/router actually worked GREAT for the first 11 days. I am just now getting the Xfinity activation page — when trying to access my browser. My landlords don’t mind me hopping on their network – its just that the signal is less than ideal. It was a no-brainer to hook up my own modem & router! I’m going to check with my employer’s help desk tomorrow to see if they have some geek trick to bypassing Comcast’s lame activation setup!! Definitely not interested in paying for a second internet account. Wish me luck :)

    • @Natalie What did your geek say? Did he help?

      So far I only have questions… Is it possible to bypass modem activation on Comcast page? If one already has an activated comcast modem with a certain MAC ID #1 maybe there’s a way to “pretend” the second modem has the same MAC ID? I have the same situation as you, Natalie, and so far I just purchased a 200ft outdoor ethernet cable to link my modem on the first floor with Roku 2 on the second floor because my Airport Extreme doesn’t cover the most distant point on the second floor well.

      • 2 year ago (2010) i had 2 modems on same coax; all working.
        then cc introduced this activation page and one of my modem stopped working.
        Tried adding the modem back and activation page said that if i am upgrading my modem. i said no (thinking that it will disable the other one)
        So I took out the modem for about a year
        A week ago, added TV box and upgraded the internet to 50mbps.
        Then added that modem back.
        When i tried to go to the web, activation page came up with TV and Internet box activation :D
        I hit activate and voila! I have 2 modems back in action :D

        Now if i login into the cc website i see my 2 modems (+1 imaginary modem) and TV box.

        I was able to get this 3rd modem added thru chat support :D

        Try this:
        Take out the first modem.
        Tell them you are not getting any signals on the main box.
        Tell them you have another box you bought and would like to try that.
        Give them the MAC and S/N.
        Tell them it didn’t work (lol)
        Close session
        Plugin in the second modem (lol)
        And try your luck!

        Have fun!

        • my setup right now:

          Main line splits into two lines.
          1. Goes where main TV is located. And again cable splits and connects to a TV and a second Modem.
          2. Goes to first Modem.

          I have a wireless router on each modem.
          Helped my TV and nearby devices with wired connections.
          And 2 wireless AP for maximum strength of wifi in my 2 story house :D

          Very happy again after a yr :D

          When i lost my 2nd modem at first. I used dd-wrt on one of the wireless AP to run as a repeater (didn’t work too well but I had connection. lol)
          I was planning to wire with cat6 but good thing i checked and 2nd modem worked.
          So all good for now.

          And that’s my story :D

  7. I bought a motorola modem to not have to rent the comcast modem. Doesnt work that way. Everyone I talked to gave me a different answer. I have the triple play and now that my new modem is connected I have no phone service. Is there such a cable that is Y shaped or dual so that I can connect my cable from the wall into my new modem and comcasts modem. thanks

    • You can get an RF splitter at Radio Shack to divide the signal from the coaxial cable from the wall to two other devices with their own cables. This is the same kind of splitter you would use to hook up both your TV and modem to one cable outlet. However, it’s not going to help your situation. Each modem has its own “MAC id” that identifies it to Comcast. They will have replaced the MAC id of your old modem with the new one. The old modem won’t work anymore.

      I only have Internet from Comcast, not Triple Play, so I have no advice to offer on your phone problems. I can say that I use Phone Power for IP telephony over my Comcast Internet connection. I have been pretty satisfied with it.

  8. You can run 2 different modems on the same account. One has got to be set up as a test modem in which Comcast tech that comes out can make a call to add the mac address to your account. As i have been running for the last 6 months the data usage is recorded on one account. one bill i rent one and own the other with over 999G of data used per month

  9. Weird, I have Time Warner Cable… and have their Arris DOCSIS 3.0 modem hooked up in my office… with the voip phone line. I wanted ethernet in the bedroom for my PS3 (hey, call of duty, can’t mess with Wifi)…. I got a Motorola SB6120 also and just called TWC…. told them that I was using the Arris for the telephone and wanted to use my own modem for the intenet…. they took the MAC ID and activiated my own modem and left the Arris fully connected… so basically I have two cable modems in my apartment both of them pulling 30 Mbps down and 5 up…. Don’t know if I am lucky or what, but it CAN be done….. I have THEIR modem and MY modem both hooked up at the same time.. getting pretty fast speeds… I was going to try and add a 3rd but figured I better not push it :P

  10. It seems a variant on this technique could allow you to be constantly switching between “new” and existing Comcrap accounts to allow yourself to always get “new customer only” promotional (ahem -predatory) pricing. It would just require owning 2 cable modems. Here’s an example – your first year or 6 month promotional pricing is about to run out. Hook up the second cable modem, and open a secondary account (ideally in a different family members name). Once the “new” account is active, you can cancel the original account. When that account is nearing the end of promotional pricing, you hookup the original modem, call up and activate a “new” account. Continue cycle every 6 months to a year (depending on predatory pricing deal length). If you can bypass the activation fees (or even if you can’t) you’re probably still coming out on top and not allowing comcrap to discriminate against you because you are not a “new” customer.

  11. I would say not without paying an additional cost because when you added the first cable modem you had to connect to Comcast’s local server and register the mac address of the modem with them so the second cable modem would not work without registering it with them first.

  12. I currently have a phone/cable modem connected in the basement that comcast installed for their phone service. I use a seperate modem and router for wifi throughout my house. Since I have a computer in the basement am I within my rights to connect an ethernet cord to the phone/cable modem from the computer in the basement?

  13. Have triple play with HD Preferred XF TV, performance internet, and telephone. Decided to buy my own cable modem to save $$$. Bought same RCA DHG535-2 Cable Modem from ebay used for $35. At $7/mo, the payback is 5 months. Swapped out modems – TV programming still working, but phone and internet cut off. Next, called Crumcast customer service, of course should not have started there. Was sent to tech service. Waited 20 minutes for someone to come on the line. Once tech pick up it was very painless – the tech was great and very friendly, not pushy. Internet came right up, however, the phone did not come back up, so transfer to customer service voice activated help line. Clocking 38 minutes by this time. Couldn’t be fixed automatically, so transferred to an account assistant…”please wait….please wait….your call was unable to be completed – please hang up and dial the tole-free number again”, right at 40 minutes. Sheesh.

  14. I have Brighthouse and tried to do the same thing cause I wanted two hardwire connections one for amart TV and the other for internet and wireless in 100 ft away locations and wireless wasn’t able to stream vidio to my smart TV that far away. Had two techs from Brighthouse tell me lat night I could do it. Had two tell me today I could not without paying for two IP adresses, I do have a Vonage box as well so Mybe the guy who told them one was for Voip would work. My Vonage box has and eithernet hookup instead of coax connection. I might just try that. BTW I had to make four phone calls to get my Motorola SBC6580 hooked up and Im having issues with dropped wireless and having to re enter the stupid 20 digit Key. My Belkin router worked much better and I didn’t have to have a Key. It is so hard to get good customer service anymore.

  15. I got lucky it seems. I recently purchased a new cable modem and called and had it added and Comcast left the original one on the account. At first I just ran with one modem but I decided to just try the other modem on my bedroom cable connection and it works fine. It is very nice having a second cable modem.

    • Hello FR. Can you be more specific. What type of modem did you buy? Was the modem wireless? Did you buy it from Comcast? Was the original modem a Comcast modem? Which one of the two did you try first? I have internet and cable with comcast. I’m trying to use and old comcast modem I had laying around as a second modem but I keep getting registration page. Thanks for the help.

  16. Well, I have 2 modems in my apt and its a bit awesome. I have multiple devices that work poorly over wireless (e.g. Denon In-Command Series HT) and had to direct connect it via ethernet. Also run Apple TV, XBox, etc….given the hard wiring of the Denon, I had to move my wireless router (apple exteme base station) right next to the stereo and the new location signal wasn’t strong enough to stream netflix thru the Xbox in the kids bedroom on the other side of my unit….(thick walls I guess)…so I wanted to connect the xbox directly to the modem like I did to the HT system….then by chance Comcast sent me an upgraded modem to replace my old one….instead of replacing, I just activated it to the cable line coming in near the xbox room (no splitter needed) per the instructions (connecting the ethernet cable from the mdem directly to my PC for activation)…then presto, I have two modems working and they are both hard wired thru ethernet cables to the devices that required it and to my wireless router for all other computing needs….whole process took about 20 mins….

  17. When you call Comcast to get the new internet only account how did you get past the street address question?

    I have a situation where I am renting the top part of my house and keeping a basement apartment for myself where I want to keep cable modem internet service. I called Comcast to ask what how to handle my current service if my renter also wanted Comcast services and they told me that I could not have two active accounts at the same physical address.

  18. Wow, it actually worked for me. I’m able connect the leased Comcast techicolor tc8305c modem/routet in one cable jack and my owned Motorola 6121 surfboard modem plus apple airport time capsule router in a different cable jack.

    Although I originally planned to use the leased modem/router just for phone, it’s included with wifi router already and I needed to keep the apple airport time capsule for backing up my computers anyway. Since the moto 6121 and apple airport time capsule showed consistently faster speeds than the leased Comcast modem/router (tested many fifferent ways), I mainly use that for my Internet connections. But the point is that I have the option to use either of the two connections, which increases my range.

    Just a note, I activated my owned modem with comast first, then they added the leased one during install of phone. So my owned one remained on my account rather than trying to add it later.

    Best of luck.

  19. I was told by a Comcast installer about a dual accounts option meaning that if I have a family member i.e. my father in law who has a Comcast TV account at his residence, that at our residence we can have a separate Comcast TV account. His bill will not change he will receive his bill and the one for residence will come to our place. But when I called the lady had no idea what I was talking about. Does Comcast offer something like this.

  20. Comcast installed cable/phone/internet on one side of my son’s room, but his gaming computer is not WiFi, so we need to hard wire his computer with the Ethernet wire from Comcast Router to his computer. The problem is Ethernet wire is crossing the room and we could trip. Should I run Ethernet wire through the celling and wall? Or is their an easier way.

    Thank you in advance. Non Tech Mom, here!

    • Just use a longer Ethernet cord that can run along the base of the walls/edge of the room rather than cutting across the middle of the room. Cord should be pretty cheap -ebay may be the least expensive place to get it or shop on bigger internet. Hope your son enjoys and appreciates his mom’s efforts (speaking as mom of teen son).

  21. Comcast is giving me the run-around….
    There is already Comcast internet at the house we’re moving into and we wish to add our own (already existing) internet/phone when we move in. (In effect a simple transfer).

    Comcast is saying we cannot have two separate internet accounts at the same address…….

    How true is this? I read different stories on this, some people able to achieve success and some meeting the roadblock I’m running in to….

    It’s technically possible, there ARE people doing it, so what gives?
    Any advice on this?

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