How to Replace a Cable Gateway with Your Own Modem

A typical cable modem.

If you’re using Comcast cable Internet (a.k.a Xfinity), check your bill, you might be paying around $15/month “equipment rental” fee. If so, replacing the provider-supplied 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 grade of your liking. And, in many cases, retailed hardware can improve connection speeds.

This post will walk you through the process of replacing a cable provider-supplied equipment with your own.

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Note: I wrote this post based on an Xfinity Internet plan, but if you use any other residential cable Internet service, such as Time Warner Cable, Cox, Charter, and so on, the process is similar. Also, while this post is about replacing an existing device, it also applies to set up a new service. In this case, make sure you choose not to use the provider’s equipment when ordering the service.

A. Identify your current cable Internet’s modem/gateway

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

First, are you currently using a modem or a gateway? Most users have a gateway instead of just a modem. If so, they will need a new Wi-Fi router in addition to a new modem, or they can get a retail gateway. The reason is a network needs a router — a gateway combines a modem and a router into a single box.

Tip on Modem vs. gateway: Take a look at your internet box, the one that connects to the service cable. If it has just one network port on the back, then it’s a modem, if it has more (typically four) then it’s a gateway. A gateway is generally much bigger than a modem. For more, check out this post.

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.

B. What cable Internet equipment to get

There are many options for retail modems, routers, and gateways. You’ll need a set of a modem and a router, or a single gateway. Note that if you also have a TV plan from your provider, the Internet modem has nothing to do with that. TV generally uses separate hardware.

The AmpliFi Alien is a cool and super-user friendly home Wi-Fi 6 router.

What’s the best Cable Modem?

Modems are simple devices and tend to work similarly. What set them apart mostly in their standard — currently DOSIS 3.0 vs. DOCSIS 3.1 — and speed grades. Generally, you just need to worry about the latter, and a typical one from Netgear, TP-Link, or Motorola will likely work out.

Those without a cable phone service can get any modem that can handle the Internet speed of the plan, or faster, and work with the provider. If you’re a Comcast (Xfinity) customer, here’s the list of the approved modem (gateway) for your address based on your broadband speed. (Note: You might need to sign in with your account.)

The key here is to get what you need, it doesn’t hurt to get the fastest modem out there, but if you don’t have an internet plan that requires it, you’re just wasting your money. But if you want to make sure, get a DOCSIS 3.1 modem that’s capable of 1 Gbps (or faster).

If you need a phone-capable modem, there are fewer options. In my experience, either the ARRIS Surfboard T25 or the NETGEAR CM500V is an excellent choice. Keep in mind that a phone-capable modem will work even when you do not have a phone service plan. So get one if you intend to add a phone service later.

By the way, an used or refurbished modem will work the same as a new one. Just make sure you get one that’s in good physical shape.

Once you’ve settled on a modem, it’s time to pick a router.

What’s the best Wi-Fi router or mesh system for cable Internet?

All routers, or mesh systems, work the same with any internet source. So if you get a good one, it’ll be good no matter who your provider is and what type of connection you have.

What’s also always true is the fact the router is the one that decides the performance of your home network. Just pick one that fits your needs and budget. Not sure what you need? This post on how to pick the best router for your situation will help.

Or, you can follow the general direction:

  • If you just need a reliable able network and don’t want to spend too much? Get one of these Wi-Fi 5 routers.
  • If you’re ready for the latest and greatest, get one of these Wi-Fi 6 routers. For those living in a large home, a Wi-Fi system is definitely a must. In this case, also consider one of these Wi-Fi 6 mesh systems.

Retail gateways are available, too

An ideal setup is a modem and a router. However, if you don’t want more than one box at your internet drop, you can get a gateway (router/modem combo) of your own.

Keep in mind, though, that if you get a gateway, you’ll have to replace the entire thing when you want to upgrade your network, and not just the modem or the router portion of it.

If you don’t have phone service, the ASUS CM-32 Cable Modem Wifi Router is an excellent choice, it’s essentially the RT-AC88U plus built-in cable modem. On the other hand, if you have phone service, the ARRIS Surfboard SVG2482AC worked well in my experience. Again, a phone-capable gateway will work even when you do not have a phone service plan.

If you live in a large property and need a mesh-ready gateway, Netgear’s Orbi CBK40 is the only option for now. It’s available as a single gateway or a mesh system. It doesn’t support phone service.

C. How to set up new cable Internet equipment

No matter what you get, be it a simple 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.

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

Cable Internet setup: What you need

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

  • A computer with a network port. If you have one of those laptops that only have Wi-Fi, get an Ethernet dongle for this job. Or, if you have an existing Wi-Fi router, you can use its Wi-Fi network — more on this below.
  • Your cable account information (account number, phone number used when signed up, home address, etc.) or the login information. In my experience with Comcast, the Xfinity username and password are enough.

Steps to replace/install a cable Internet modem/gateway

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

A typical cable hardware setup: Connect the modem (left) to the service line (white cable), and the router’s WAN port to the modem (red cable).
1. Replace the old hardware

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

2. Connect the new hardware

There seems to be a lot of text in this part and that’s because I wanted to be as detailed as possible and cover different scenarios. In reality, it just takes a few minutes. Here goes:

a. Connect the service coaxial cable into your new modem, or gateway, securely.

b. Use a network cable and connect your computer to a LAN port of the modem (or gateway). A modem generally has only one LAN port while a gateway might have a few, you can use any of them.

A couple of things to note:

  • Alternatively, if you get a new modem and have an existing router that has already been set up, you can connect the router’s WAN port to the modem, and then your computer to the router via its Wi-Fi or LAN port. Don’t do this if you have a brand-new router that’s not yet initialized. You can’t activate a modem using a router at its default factory settings. That’s because many routers require a live Internet connection (one with an already-activated modem) before you can set it up.
  • Make sure your computer and router (or gateway) have the default (auto) DNS settings, meaning it will use the DNS servers of the Internet service provider. The good news is that’s always the case unless you have changed the DNS manually. Using customized DNS will cause the activation process to fail. So use the default one and you can change that later.

c. Now plug everything into power and wait for the equipment to boot up. Typically, this will take just about one minute, but you can give it a few minutes to make sure.

A bit of troubleshooting: Look at the lights on the cable modem (or gateway). You want to wait till the Online (sometimes labeled as Signal or Sync or Data) light 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 little 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.

Not the Internet light on the modem (right). It's supposed to be on solid when your broadband connection is working well.
Note the Internet light on the modem (right). It’s supposed to be on solid when your broadband connection is working well.
3. Activation

On your connected computer, launch a browser (such as Firefox, or Chrome), you will automatically get to the activation page. If not, just try going to any website and you’ll automatically reach that page. Now follow the onscreen instruction and log in your account. See the screenshots below.

The activation process is self-explanatory.

If you don’t have an account or don’t remember the password, you can choose to use the account number instead and go through a few other steps of verification. After that, the new equipment will then be activated automatically and will restart itself.

The underside of a cable modem. Note its MAC address.
The underside of a cable modem. Note its model number and MAC address.

If for some reason, the online activation fails, which rarely happens in my experience, you can call your provider. In this case, have the modem/gateway’s serial number and MAC address ready. You can find this information on the bottom (or the side) of the device. The support technician will activate the equipment for you at their end.

The final step

And that’s it. Now your new equipment is ready. If you just activated a modem and have a new router, you can now plug the router’s WAN port into the modem’s LAN port and follow this guide to set up your home network.

Using your own modem, you have the options of replacing the router — and upgrade 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.

Dong’s note: I originally published this post on February 15, 2018, and updated it on March 20, 2020, with additional relevant information.

24 thoughts on “How to Replace a Cable Gateway with Your Own Modem”

  1. 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.

    • 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.

  2. 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)

  3. 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!

    • 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.

  4. 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?

  5. 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.

  6. 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.

  7. 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?

    • 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. 🙂

  8. 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!

    • 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.

  9. 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.

    • 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.

  10. 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.



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