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Comcast Xfinity Cable Modem Activation: How to Ditch that ISP-Provided Gatway

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If you’re using cable Internet, check your bill. You might pay around a $15/month “equipment rental” fee.

If so, replacing the ISP-provided equipment with a cable modem of your own will eliminate that monthly cost. Over time the saving will more than pay for the hardware you need to buy upfront.

Using your modem brings about other advantages, too. You then can pick a router, or a mesh system, with features and performance grades to your liking. And in many cases, retailed hardware can improve connection speeds.

This post will walk you through replacing cable-provider-supplied equipment with your own. Before continuing, make sure you brush up on the Cable modem standards.

Motorola MB8600 Cable Modem
The back of a typical cable modem — note the coaxial connector.

Dong’s note: I originally published this post on February 15, 2018, and updated it on January 8, 2022, with up-to-date information.

How to replace (Comcast Xfinity’s) Cable gateway with your own modem (and router)

Some of you might be happy with your ISP-supplied hardware and don’t mind paying the extra for the convenience and some potential perks. That’s fine with me. But in that case, you should check out my take on how to get the best out of that gateway instead.

Extra: The benefits of using an ISP-supplied gateway

While it’s clear that it’s best to use your equipment, there are some benefits to using a gateway provided by your Internet provider.

Here are a few examples:

  • Ease of use: You don’t need to do anything. The provider will set up the home network work for you and manage the hardware, including firmware updates, troubleshooting, etc.
  • Less cluttering: You only have one hardware box instead of two. (A retail gateway applies, too.)
  • Hassle-free hardware replacement: If the gateway dies, call the provider, and you’ll get a replacement pronto — all free of charge. The provider also upgrades the equipment when need be.
  • Easy management: With some providers, you can manage certain aspects of your home network, like changing the Wi-Fi password, via your online account. (That is if you’re OK with the potential privacy risks.)
  • Unlimited data cap: Some providers, such as Comcast Xfinity, give you half the cost ($25 vs $50) of an unlimited monthly data cap when you use their gateway.

In short, using ISP-proved equipment is not all bad. The benefits are enough to justify the monthly “rental” fee for some.

For those who want to take control of the equipment, remember that what you’re about to read is based on a Comcast Xfinity Internet plan. However, the process is similar if you use any other residential cable Internet service, such as Time Warner Cable, Cox, Charter, etc.

Finally, while this is about replacing an existing gateway, it also applies when upgrading a modem or setting up a new service.

With that, let’s get our hands dirty with these three parts to replace that ISP-supplied equipment with your own.

A. Identify your current cable Internet modem/gateway

If you’re about to replace a provider’s equipment, there are two things to remember.

First, are you currently using a modem or a gateway? In most cases, you have a gateway instead of just a modem — in recent years, IPS only provide gateways so they can keep tabs on their subscribers. If so, you will need a new Wi-Fi router and a new modem, or a retail gateway.

A network needs a router — a gateway is a modem and a router in a single box.

Second, do you also use phone service with your cable internet provider? If so, you will need a phone-capable modem/gateway, which is typically more expensive.

Generally, I recommend getting just the Internet from the service provider and avoiding a package deal. After that, use a different Voice over IP phone service, or skip it and use only your cell phone, and a streaming TV plan, such as YouTubeTV.

That said, this post will focus on the scenario where you get just a Cable modem. However, if you get a retail gateway, the process is similar.

B. Get yourself a modem

To know which modem you should get, check out this post on Cable vs Fiber. However, this decision depends mainly on the broadband connection download speed. Specifically:

  • 500Mbps or slower: Get a DOCSIS 3.0 modem. A DOCSIS 3.1 one is not necessary and might not work.
  • 500Mbps to sub-Gigabit: Either will do, but it’s better to go with DOCSIS 3.1.
  • Gigabit for faster (Gig+, Multi-Gig): DOCSIS 3.1.

Need to make a quick decision? Check out my top Cable modem picks.

Best Cable modems: The top five real-world tested options

If you need a phone-capable modem, the ARRIS SURFboard T25 is one of the best among only a handful of options.

C. How to set up a new Cable Modem (for Comcast Xfinity)

No matter what you get, be it a simple cable modem, a phone-capable modem, or a gateway, the setup process is the same. You need to activate your equipment on the provider’s network.

Netgear CM600 Cable Modem 14
A typical cable hardware setup: Connect the modem (left) to the service line (white cable) and the router’s WAN port to the modem (black cable).

These steps, by the way, apply only when you want to activate a residential Internet plan. You’ll likely need to call the provider if you have a business plan.

Also, they apply mainly Comcast’s Xfinity Cable Internet plan, but the process is similar if you use another Cable provider.

Update

Initially, I recommended that you use a computer connecting to the Modem via a network cable and perform the activation via a web browser.

However, since mid-2021, Comcast has slowly phased out this activation method in favor of the Xfinity mobile app. Specifically, I found out that the web browser no longer worked during the testing of the Netgear CM1000.

While the old method might still work for some, using the app is the way going forward.

(Comcast Xfinity) Cable Internet setup: What you need

To activate a piece of new equipment, you need two things.

  • An Internet-connected phone or tablet with the Xfinity mobile app on it. You can download the app from the App Store of Apple or Google.
  • An existing account with Xfinity. You should have one when you sign up for the service. This account includes a username (an email address) and a password. If you have multiple users in your account, make sure you use the email of the primary user.
  • Note the MAC address of the modem. The MAC address is generally printed on the side or bottom of the modem. See the photo below for an example.
MAC Address on a Cable Modem
The MAC Address on a Cable Modem. You only need to note the number and letter and ignore everything else, like the dashes (-).

Steps to replace/install a Cable Internet cable modem

Again, relatively specific steps apply to those with a Comcast Xfinity Internet plan. If you use a different provider, the process varies though likely similar.

I. Remove the old hardware

Remove the existing gateway or cable modem. (Make sure you return the equipment afterward to have the rental fee removed from your account.)

II. Connect the new hardware

Place the new modem in place of the old equipment.

  1. Connect the service coaxial cable to your new Cable modem (or retail gateway).
  2. Connect the cable modem’s LAN port to your router’s WAN port.
  3. Connect them both into power and turn them on.
Motorola MB8600 Cable Modem 9
Note the Internet light on the cable modem (second from bottom). It’s supposed to be solid (green, blue, or white) to indicate your broadband connection is working well.
A bit of troubleshooting

Look at the lights on the cable modem. You want to wait till the Online led (sometimes labeled as Signal or Sync or Data) is on solid.

The color of this light varies depending on the modem, but it tends to be white, blue, or green, and it almost always takes the symbol of a tiny globe. If this light doesn’t turn on, that means there’s no Internet signal. Check to make sure the coaxial cable is plugged in correctly, or call the provider.

When the lights are in good shape, you’re ready for activation. If the signal light is not solid, check the cable, or call the provider to report the issue.

III. Activation (on a Comcast Xfinity network)

Typically, no matter who your provider is, you can call their technical support line, give them a new modem’s MAC address and get it activated for you.

However, you can also do that yourself, at least when you use Comcast Xfinity.

Here are the steps — make sure your mobile device (phone or tablet) is connected to the Internet, likely via cellular signals.

Comcast Modem Activation
How to activate a Cable modem with a Comcast Xfinity Internet plan, steps 1 to 3.
  1. Run the Xfinity mobile app, sign in with your account, then tap on the head and shoulder icon (top left corner) to open the Account section.
  2. In the Account section, scroll to Activate xFi Gateway or Modem. Tap on it.
  3. Tap on Your Own Modem.
  4. Tap on Start Activation. The app now will run you through a few steps on connecting the hardware, which we already took care of in the previous section. Keep tapping on Next to run through it and then on Ready to Go at the end.
  5. Enter the MAC address of the modem in the box. Enter just the numbers and letters of the MAC — ignore the dashes (-) or colons (:) that separate them. Make sure you don’t make a mistake. So, if a MAC is D4-FB-6A-7C-31-B4, you enter just D4FB6A7C31B4 and nothing else.
  6. Click on Next and wait for the activation to finish.
Comcast Modem Activation Final
How to activate a Cable modem with a Comcast Xfinity Internet plan, steps 3 to 6.

The activation process will take from five to 10 minutes to finish. During this time, the modem will restart, even a few times. Once it’s completed, manually restart your modem and your router.

And mission accomplished.

The final step

And that’s it. Now your new equipment is ready.

Using your own modem, you have the option of replacing the router — and upgrading your home network — whenever you’d like.

And when you do, note that you should restart the cable modem after you plug the new router into it for the two to work well with each other.

The takeaway

Cable providers generally want you to use their equipment. The fee aside, that allows them to have some or complete control over your network, depending on the equipment being used.

That said, using your own modem and router allows you to take over the control, as well as the responsibilities in regard to your security and privacy.

Both situations have their pros and cons, but the latter is a no-brainer for me personally.

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47 thoughts on “Comcast Xfinity Cable Modem Activation: How to Ditch that ISP-Provided Gatway”

  1. Hi, Dong…..wondering if you’ve any experience using a cable splitter to use the coaxial for the cable modem and for a cable box. Any know performance issues that you’re aware?

    As always, thank you.

    Brad

    Reply
    • I’ve used that, Brad, with no performance issue when I had a 600Mbps plan but I haven’t tried with faster speed grades. However, you should really ditch the Cable box and go full streaming, like YouTube TV, the way it should be in the 21st century. 🙂 Do it!

      Reply
        • Do it! Imagine you can watch your TV anywhere you are, including when you sit in your car waiting to pick up your kids and then continue with the program on your big TV when you get home, or on your computer’s screen, etc. There’s nothing to negotiate. Pick whichever you want, Hulu, YouTube TV, etc. And it’s cheaper than Cable. It’s a no-brainer.

          Reply
          • Return poster from this thread. initially I ditched the rental equipment and used my own. It gave me more control with cost savings. I’ve now dropped Comcast altogether for ATT Fiber. Paying $80 a month for 1G up & down, no data cap charges and HBO MAX included ($10 a month savings). I use YouTubeTV and have no complaints. Drop cable and go fiber + a la carte for your streaming.

  2. I need a 3.1 docsis emta xfinity approved modem. I don’t need a gateway/router. There seems to be only 2 available at this time. The Netgear CM2050V or the Arris T25. No retailers seem to have any other models. I know the Arris T25 has the puma 7 chip and some people have had problems with it but many haven’t. The T25 is about $200 cheaper right now. Which makes it very attractive. Has Arris corrected the firmware since it was introduced? If it has, does xfinity to push it through? Do you have any thoughts on the T25?
    Thanks!

    Reply
  3. Good information. Thank you!. However, owning your own modem isn’t perfect: My ISP refuses to update the firmware on my cable modem or do any line debugging because they don’t own the modem (even when it’s identical to their rental modem). How do you handle this situation, or is a regulatory loophole that we simply have to live with?

    Reply
    • You can update the firmware yourself, Joe, via the modems interface. Most of the time, you won’t need to do that at all.

      Reply
      • I have to disagree. For combined modem/router devices, you may be able to update the router portion of the firmware, but NOT for the modem section. And the user cannot update any firmware at all for cable modems alone. This process was set many years ago to prevent people from stealing internet service. Unfortunately, it also gives the ISP full control of your device and the reason to deny line debugging if they chose.

        Reply
        • Interesting. I actually didn’t know that. But generally, folks get a modem to get connected, not to debug or update the firmware. If that’s something really important to you, I’d recommend getting the ISP-supplied hardware. There are other benefits, too, as mentioned in this post.

          Reply
  4. Hi Dong,
    I understand that we have more choices and control if we provide our own hardware instead of renting from Comcast. But I’m wondering if you know what the comparable performance is with their recent Xfi XB7 gateway for gigabit service. Do you have a sense of how much we would have to spend to get a gateway or modem/router combo that would perform better?

    I like your sentiment of not over-paying now for “future-proofing”, so would that make the argument to lease from Comcast and get a new gateway from them every 2 years or so?

    Thanks for helping us all!

    Reply
    • Any of the modems I recommended in this post will outdo the XB7 in broadband speed, Mike. After that, you can get any router or mesh system of your choice. Links in the post, too.

      Reply
  5. Dong Ngo,

    My router is currently located in my living room next to my modem and I’m trying to extend my network wirelessly to a back bedroom so I can set up my home office. I know I should replace my router anyway because it’s most likely rented. However, I need to be able to connect my work phone to a router via ethernet cable. So I’m trying to find a router/mesh system that I can connect an access point (With an ethernet port) in the back bedroom without having to run an ethernet cable from the router location in living room under the house (Older ranch with a crawl space) that will allow my phone to work effortlessly. My work phone system utilizes a phone answering software program on our computers so I have to be connected thru an ethernet cable connection. TYIA

    Reply
  6. Hi Dong, I love your thorough and informative postings and reviews.
    I now understand the cable modem situation.
    I have Verizon FIOS Giga service (modem). Is there any alternative modem/router for people with that service?

    Thanks, Reuven

    Reply
  7. Something your readers may want to consider, when looking replacing the Xfinity gateway with their own equipment. To make a long story short, some high bandwidth customers could end up paying more.

    Unlimited internet is $50/ mo
    If a customer has 300mb/s or faster connection they can get xfi advantage which includes XB6 or XB7 gateway AND unlimited data for only $25/mo. A savings of $25/ MO. At $300/yr savings one can justify picking up vert high high end router/mesh system.

    Reply
    • You forget the rental fee, Sky. And you don’t need unlimited, you can just pay for the extra amount when/if you go over the limit. The data cap is a scam anyway.

      Reply
    • The prices have changed and the differences are less. For those who need unlimited Internet the cost is now only $30 a month for unlimited and leasing a modem at $14 a month and unlimited is $11 a month for For a total of$25 it is called Xfi complete. The difference is now less. But the cost does end up as being $5 more per month if unlimited is necessary For the privilege of buying your own equipment. Unfortunately turning the cost savings of owning your own equipment upside down. But there is clearly some benefits to owning your own equipment, Namely performance and control.

      Unfortunately wether you believe unlimited is a scam or not is irrelevant for this part of the conversation. Could be a fruitful conversation otherwise.

      Reply
  8. Hi, I have Arris TG3482G provided to me by Xfinity but can’t change the DNS settings which I would like to do. I bundle cable, internet & telephone service with Xfinity so if I’m understanding currently I need to buy both a router and modem? Or do I only need a gateway device? (Sorry, I have very limited knowledge on this stuff)

    Reply
  9. Hey Dong! I have the Motorola (Arris) SBG6782-AC Combo Modem/Router with built-in MoCA back in 2014, based on your excellent recommendation. Is there an updated version of this now? Complete with the built-in MoCA (which I love)?? Thank you!

    Reply
    • That one should still work fine, Thomas. I think eventually, there will be a Wi-Fi 6 version, but right now, there’s no update yet, as far as I know.

      Reply
  10. I am moving into a 600sq ft apartment soon. I will have 300mbps internet speed and want to use a wired connection for my gaming console and desktop computer. Streaming music and video will be most of the wifi load. I’m planning to purchase a 600mbps modem but when searching for a router I want something with high speeds but a large coverage area isn’t necessary. Do you have any recommendations?

    Reply
  11. You’re correct, during the setup, the gateway, or router, need to use the DNS of Comcast, which is the default, unless you have changed it. In this case you need to change it back for the setup.

    Reply
  12. I replaced my leaxed Xfinntiy Arris gatewary router with amy own Motorola MB8600 modem. Eliminated the double NAT problem my network was having with the Arris as well as giving me download speeds somewhat in excess fo my plan’a 300 MBS (the Arris was givinng less than 100 MBS).

    As far as self-activation goes, it worked when I went to Comcast activation via the Motorola site but not if I went directly to Comcast. I had no problem with having two home locations on my account. I signed in with my id and password and was given the choice of which location I was doing the activation from. I did have to change my DNS settings to “automatic”.from the dedicated Goolgle DNS server addresses I had been using.. changed back after activation.

    Reply
  13. Hey Dong,
    I’ve always been partial to the Arris cable modems. What is your reasoning for recommending the TP-Link? Better reliability or just personal brand preference?

    Reply
    • It was just the cheapest at the time I wrote the piece. I also had used many of them all were reliable. Modems are relatively simple devices and they are very similar. And of them will do. Just pick one that supports the speeds of your plan. 🙂

      Reply
  14. I guess this doesn’t apply to FIOS. I’ve got an ethernet cable coming right out of the FIOS unit right into my N66U. I do need to piggyback off the FIOS router for Video On Demand and Guides to work, but hey it gives me three more ports!

    Reply
    • No, the post applies to cable only. However, I think you can get your own FIOS box, too, and replace the vendor’s box with it. I haven’t tried that, however, since we don’t have that option where we live.

      Reply
  15. Also, depending on which region of the country you are in, if you supply your own modem, you may be eligible for a $2.50 “customer supplied equipment” credit per month. So net savings of $12.50/mo adds up quick.

    Reply
    • If by service you mean the Wi-Fi, then you should just add an access point. But it’s better if you replace the Comcast box with your old modem and router.

      Reply
  16. Dong Ngo,

    I have the Linksis CM-8 cable modem. I have it connected to my Asus RT-AC3100 and RT-AC1900P connected via AiMesh network.

    Thanks

    Reply

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