Technology Explained

5 Questions to Ask When Purchasing a New Cable Modem

Megan Ellis Updated 23-11-2018

Cable internet service providers are still the go-to for people who don’t have access to fiber-to-the-home (FTTH) or LTE. And while you can just rent modems from cable companies, there are certain benefits to buying one instead.


Since cable ISPs operate differently to other ISPs, the things you have to take into account when choosing a cable modem are not the same as for other types of modems.

Here are the top things you should consider when buying a new cable modem.

1. Is It Better to Buy or Rent a Cable Modem?

Your first consideration is whether buying a cable modem is the best decision for your own situation. If you think you’ll switch from cable internet to FTTH Cable vs. Fiber Internet: Which One Is Better? The two most common forms of broadband internet are cable and fiber. But which one is better for you? If you have the option of both, which one should you go with? Read More relatively soon, renting may be your best bet. But if you’re planning to stick with the account for over a year, buying a modem will end up saving you money.

You can buy decent modems for the same price as the cost of several months of rental payments. After two years, it’s likely you would have saved a significant chunk of cash.

There’s also the benefit that if you change your internet connection type, you can sell off your old cable modem and make some money back. If you just change your ISP, you don’t have to deal with the hassle of returning and getting a new rented modem.


It’s also important to check whether your cable provider allows customers to use their own modems in the first place. Depending on where you live, certain cable companies may not allow you to use a third-party modem for their services. In this case, you would have no option but to rent a modem from your ISP.

2. Is the Cable Modem Compatible With Your ISP?

Most cable modems work with most cable ISPs, but there are a few exceptions. Before committing to a specific product, you should check whether it is compatible with your specific provider.

You can find this information on most cable ISP websites. If you’re struggling to find the right page, just do a quick search on Google for modems for your specific cable ISP. You’ll not only find the compatible device list on your ISP’s website more easily, but you’ll also find specific recommendations from retailers.

Product descriptions for cable modems will also usually identify any incompatible ISPs.


3. Does the Cable Modem Support Your Plan’s Speeds?

You should make sure that your modem has the right speed capabilities for your internet plan. If your modem is too slow, it will essentially cap the speed of your plan and cause slow speeds in your home network 9 Things That Might Be Slowing Down Your Home Wi-Fi Network Tired of slow or spotty internet? Check these things that could be slowing down your home Wi-Fi network. Read More .

At the same time, there’s no point in getting a lightning-fast modem if you only use a 100Mbps plan, since your modem speed cannot increase the speed of your plan past its maximum allowance.

DOCSIS is the standard that’s used by cable companies to send information over the wires, and there are three different tiers: 1.x, 2.x, and 3.x. Generally, the higher the tier, the higher the performance and speed of the cable modem.

For example, a mid-range DOCSIS 3.0 modem will offer download speeds of up to 340Mbps and upload speeds of 130Mbps. High-end modems offer higher download speeds.


The number of channels on the modem will also give you an idea of how fast the modem is. Channel numbers are often listed as a number showing how many channels are dedicated to downloading versus uploading.

For example, “8×4” means that the modem has eight downstream channels and four upstream channels.

The more channels there are, the faster the speed of the modem in each category.

Compare the DOCSIS tier and channel numbers with the download and upload speeds of your plan. You’ll want to make sure your modem is fast enough to get the most out of your internet plan. But there’s no point is overcompensating dramatically, since high-speed modems come with higher costs.


4. Do You Need a Combined Modem + Router?

Nowadays, many modems come with a built-in router. This removes the need for two standalone devices and means fewer cables. But a router/modem combination comes with both benefits and drawbacks, so you’ll need to decide whether you prefer two separate devices or one combined device.

A combination device limits your flexibility in some cases. You can’t just upgrade one part of the device if you want a faster router, for example. You’ll need to buy an entirely new combination device. At the same time, it is often cheaper and easier to just buy a single combined device.

Consider your budget, whether you’re likely to need a new router anytime soon, and other factors unique to your situation to decide whether to buy a combined cable modem and router Modem vs. Router: The Differences and Why You Need Both When you're connecting your PC to the internet, what do you need: a Wi-Fi router, cable modem, or both? Here's what you need to know. Read More .

5. Is Your Router’s Ethernet Port Speed Fast Enough?

If you have a standalone router How Does a Router Work? A Simple Explanation Routers may seem complicated, but they're actually quite simple. Here's a quick guide to routers, what they do, and how they work. Read More , you’ll need to make sure your modem’s Ethernet port speed is fast enough or risk creating a chokepoint in your network.

The Ethernet port and the Ethernet cable is how your internet connection gets from your modem to your router. If this port doesn’t accommodate the speeds of your internet plan, the connection will essentially be throttled.

No matter how fast your router is, if you have a slow Ethernet port, you’ll slow down the rest of your connection significantly. So make sure the port is fast enough for your connection.

Which Cable Modems Are the Most Recommended?

A number of factors will affect which modem suits you the best. But there are a few standout brands and devices that are recommended by cable internet users.

Here are the best modems according to Amazon’s Verified Expert recommendations for each category.

The Best Cable Modem Overall: Netgear CM600


NETGEAR Cable Modem CM600 - Compatible With All Cable Providers Including Xfinity by Comcast, Spectrum, Cox | For Cable Plans Up to 400 Mbps | DOCSIS 3.0 NETGEAR Cable Modem CM600 - Compatible With All Cable Providers Including Xfinity by Comcast, Spectrum, Cox | For Cable Plans Up to 400 Mbps | DOCSIS 3.0 Buy Now On Amazon $53.51

Dubbed “the best modem for most people”, the Netgear CM600 balances performance with affordability. It also has the benefit of being compatible with most cable companies, making it a good choice for cable internet users in general. However, it is not compatible with Verizon, AT&T, or CenturyLink.

With DOCSIS 3.0 and download speeds of up to 960Mbps, the modem also accommodates most internet plan speeds.

The Best Budget Cable Modem: Netgear CM500


NETGEAR Cable Modem CM500 - Compatible With All Cable Providers Including Xfinity by Comcast, Spectrum, Cox | For Cable Plans Up to 300 Mbps | DOCSIS 3.0 NETGEAR Cable Modem CM500 - Compatible With All Cable Providers Including Xfinity by Comcast, Spectrum, Cox | For Cable Plans Up to 300 Mbps | DOCSIS 3.0 Buy Now On Amazon $13.19

The Netgear CM500 is the more budget-friendly cousin to the CM600. While it sacrifices speed in favor of affordability, its maximum download speed of 686Mbps is great for customers on cheaper cable plans.

However, it’s recommended for people who have cable internet plans of 300Mbps or lower. With DOCSIS 3.0 functionality and 16 downstream channels, it also won’t lose ISP support, which is a risk for certain lower-end devices.

The Best High-Performance Cable Modem: Motorola MB8600


MOTOROLA MB8600 DOCSIS 3.1 Cable Modem, 6 Gbps Max Speed. Approved for Comcast Xfinity Gigabit, Cox Gigablast, and More MOTOROLA MB8600 DOCSIS 3.1 Cable Modem, 6 Gbps Max Speed. Approved for Comcast Xfinity Gigabit, Cox Gigablast, and More Buy Now On Amazon $159.99

If you want a cable modem with high speed and performance, the Motorola MB8600 comes highly recommended.

Considering that it accommodates speeds of up to 1000Mbps, you don’t have to worry about it slowing your connection down. The modem is compatible with gigabit internet plans such as Comcast Gigabit and Cox Gigablast.

High performance comes at a higher price, but this modem will be future-proof for at least a few years.

Should You Upgrade Your Wireless Router?

Now that you know what to consider when buying a cable modem, you should consider whether a router upgrade is a good option too.

While the modem is the main facilitator of your internet connection, your router is where most of your network’s coordination takes place.

If you still need to be convinced of the benefits of a new router, check out our guide on why you should consider upgrading your Wi-Fi router 6 Reasons to Upgrade Your Wireless Router Is your wireless router old and outdated? You may be missing out on several newer features that can improve your connection quality and make your life easier. Read More .

Related topics: Bandwidth, Buying Tips, ISP, Router.

Affiliate Disclosure: By buying the products we recommend, you help keep the site alive. Read more.

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  1. David Stamps
    November 16, 2016 at 7:17 am

    I just started looking to buy my own cable modem. My ISP is Time Warner (changing to Spectrum). They gave me a list of "internet compatible" units they have certified. I have a telephone/internet/TV bundle. Right now they charge $10/month rent for their modem. If I install my own "internet" modem, they want me to keep using their modem for phone service, but they will eliminate the rental charge. I will have to use a splitter to connect both devices to the cable outlet. The "nice" feature of their plan is that if I ever have problems with my own modem, I can call and have their modem reactivated for internet service (for a rental charge, of course).

    Do you know of any potential "unintended consequences" of this plan?

    • Dann Albright
      November 28, 2016 at 2:33 am

      It seems a little strange, but nothing stands out at me as worrisome. Especially if they're not charging you for it. I suppose using their modem might open you up to more surveillance by your ISP, though. Are you using your phone service?

  2. john laiche
    October 21, 2016 at 8:46 pm

    Thanks for the response. Yes, I did notice the author's name at the top of the story. My question was mostly rhetorical. If one is comparing different cable technologies, of course MODEMs may not transfer. Such as with IP-TV vs. traditional broadband TV distribution. Sort of the obvious, but I guess if someone really does not understand ...

    The sad part is that cable companies make folks believe that they, the Customer, must buy from them, the cable providers. In many instances the cable provides seem to procure a lesser device. Case in point is with Cox. They sell a Cisco device that Cisco says supports multiple SSIDs, or wireless networks. The implication is that at least one primary and one guest network can be set up. Not so. Cox does not support a guest network despite the fact that their web site leads the Customer to believe this is supported. I called them to task on this issue and wasted almost an our of my time talking to at least 4 folks that really could not give me a straight answer. It just burns me when straight answers are not provided. Sad state for many Customer Support sites, in all areas.

    BTW, your web site in the sig line doesn't appear to show up any more -

    • Dann Albright
      October 26, 2016 at 9:44 pm

      Yeah, I discovered that recently. I think it's a DNS thing. Will be getting it back up soon!

  3. john lll
    October 20, 2016 at 10:10 pm

    Who write' this foolishness? Item #1 shows that the writer does not even know the differences in service providers. At&T technology is not the same as traditional "cable" ( e.g. Cox, Shaw, Time Warner, etc) providers. Of course the modems will not work in all situations.

    • Dann Albright
      October 21, 2016 at 8:15 pm

      At the top of every article on our site—and pretty much every other site on the internet—you'll find the word "By" under the title, followed by the author's name. That's who wrote the article.

  4. Julia E
    October 6, 2016 at 7:12 pm

    Question - I am normally a Comcast customer, but am switching over to Century Link simply because it's cheaper. I have a Motorola SURFboard SB5101U cable modem and I am purchasing a 40 Mbps internet deal through Century Link. I do not have a phone jack on my cable modem. Can I simply get a Ethernet adapter to plug into my modem and connect with my wireless router? How will doing this affect my internet speed? Would you recommend getting a different modem? Thank you!

    • Dann Albright
      October 21, 2016 at 8:14 pm

      I think your best bet here is to get in contact with CenturyLink. I could make some guesses, but they'll definitely have the answers!

  5. Calvin Clausnitzer
    August 30, 2016 at 9:28 pm

    Just an additional information, the netgear cm400 would be the equivalent to the arris sb6141. The cm500 has twice the speed.

    • Dann Albright
      August 31, 2016 at 6:56 pm

      Thanks for the tip!

  6. Gajan
    July 26, 2016 at 4:34 am

    I have a "NETGEAR - Wireless-AC1750 Dual-Band Gigabit Router". I just realized that ISPs in Minnesota (Charter, XFINITY, Centurylink) work with only Cable modem. Considering that the Router is good, would I have to invest in an expensive cable modem? Any recommendations will be helpful. Thank you.

    • Dann Albright
      August 11, 2016 at 2:32 pm

      You'd have to ask your ISP for details, but you should be able to use any modem with that router. Grab one for $100 or so and you'll be set! (And saving money within a year.)

  7. Anthony
    July 19, 2016 at 11:01 pm

    Anyone know if Mexico Izzi Cable company supports American Modems. They are giving me 100mbps download with 5mbps upload. Its so sad so I want to maximize where I can.

    Author, you said it worked for someone in you have any specifics?


    • Dann Albright
      July 25, 2016 at 7:58 pm

      I don't have any specifics, sorry. I think you might have better luck on Reddit or a local forum for getting a good answer to your question, though.

  8. Brad
    July 19, 2016 at 12:33 am

    I already own my cable modem and my provider also offered me a package which included VOIP which I don't need or want (happy using Ooma). They said at first I HAD to either buy a modem with phone ports or rent one from them. They couldn't activate this bundle if I didn't have a VOIP modem.
    I asked what if I attached a VOIP modem to get set up, and then later replaced it with my old non VOIP modem -- would that work? After some checking the agent came back and said he was able to do the bundle for me even without requiring a VOIP modem (I would still have VOIP service plan but just not use it).
    In case this happens to anyone else, keep this in mind - they can be flexible if it's in their interest!

    • Dann Albright
      July 25, 2016 at 7:58 pm

      Thanks for sharing this experience; I'm sure others will find it useful!

  9. Gavin McNabb
    July 14, 2016 at 3:53 am

    hello and thanks for all the comments and suggestions on the modem/router purchasing. very helpful to someone who isn't well versed but wanting to learn before making a purchase. quick question,......I was advised by someone, when I posted a question on reddit, that the best option for setting up my "network" would be to use a 1. modem with n or a/c, 2. purchase an access point and 3. purchase a "switch". Now, I am really getting into something that I don't know about when we talk on this subject. I was just going to buy my own modem, wireless router and possibly a couple powerline devices or even signal booster/wifi extender if the situation called for it. I have a tri-level house and mainly the middle floor is main tv (for now) so i planned on connecting the modem by direct wire to the smart tv and then from modem to wifi router to send out the signal. Possibly connecting that wifi router to a powerline device so that on the ground floor i would then hook up the other powerline device (with 4 ports for future use), connect it by ethernet cable to my ps4 and be ready to go. I thought i could possibly get by without even using a powerline device and since my ground floor/middle floor are only 15 yds apart where the connections are, an extender would be enough if my ps4 isnt picking up the wifi signal to a high enough percentage. However I am now thinking about what I was told in the modem, AP and switch idea and I am completely lost. I was only getting the 15-20mbps service from TWC and I am sure I can set up the modem and wifi router but I don't know about setting up access points and switches and honestly..... do I even need all of that for the pursposes I plan on using my service for? Really, I will just use my smart tv for an occassional movie stream from netflix or Prime. I will end up using the wifi router to connect 3 tablets and 3 phones and Kindle updates too. (never at the same time however and the house has 2 retirees and I visit occasionally and use the downstairs HD normal tv to play PS4 and online gaming) So, do I need to completely ignore all the seemingly unneccessary equiptment and just go with maybe a higher end modem,(no combo modem/router I understand that clearly) a higher end wireless router and if necessary a couple powerline devices or a good wifi extender (not signal booster...Right?). Is that just perfect for what I am doing? I was also told to buy the same brand modem, router, extender, etc. Also told to use N or A/C and get something with 4 ports/2usb or whatever....I am using the advice on your post and I will probably get the netgear or Arris (85-100$) for the TWC service. I imagine it might be better to do what you advise and get a modem that can handle well over what service i am getting just in case I upgrade. Is the wifi router something that I need to look at specs on so that it will match up with the modem or get one that has a Higher speed capability? Maybe I am confused and the wifi router doesnt have anything like that even. thank you for your help. -Gavin McNabb

    • Dann Albright
      July 25, 2016 at 7:57 pm

      While I'm not an expert at setting up complicated wireless networks, it sounds to me like you'd be fine with a nice modem, router, and extenders. You won't get the best speeds, as higher-speed frequencies have a more difficult time penetrating objects, but I think it would be enough.

  10. Nick Cheney
    July 3, 2016 at 8:53 pm

    Im looking to buy my own equipment. Now my cable company has a triple play deal that includes: TV, Internet as well as phone service. Say if i buy a modem without a phone jack on it, will they not let me use it? Im not gonna be using the phone at all but the only reason Im getting it is because its something like 20 or 30 bucks cheaper to have all three rather than Internet and TV.

    • Dann Albright
      July 7, 2016 at 2:06 pm

      That shouldn't be a problem, but you'll have to talk to your ISP to make sure.

  11. PhilipJ
    May 15, 2016 at 8:15 pm

    I feel compelled to update this with accurate information, as I am someone that is submerged in the day to day realities of trouble shooting on large networks including ISP's.
    What I am adding is as good and accurate last year as it is today, DOCSIS3 has been pretty much mandated within the ISPs for some time now.

    "Whether you want to save money, improve your Internet connection, or just make it a little bit harder for your ISP to spy on you, buying your own modem is a great idea."

    Misleading to nonsense...
    Misleading #1: Leasing modems or equipment do have some positive attributes. Major one is if the device craps out, the ISP replaces without cost, quickly with no hassle. Nothing like having that wiz bang modem combo you have been led to believe is superior to everything, 90 to 180 $ cost not work the 2 week after your warranty expires. Add in cost of replacement.
    Misleading #2: Modems and equipment that you get from an ISP are inferior to what you can buy? Wow? Ok, so the ISP buys from manufacturer and leases out to customers with inferior quality. Stop and make sense of that from a customer satisfaction point of view for a minute. ISP rents inferior device, only to have to replace it because it goes down, has to send out new one, and at the same time pisses off their customer. REALLY!? Fact is most ISPs are selling or leasing modems that are from the same manufacturer that you are buying from. Typically Motorola or Arris... which are one in the same. Arris owns Motorola.

    REALLY Misleading #1: All ISPs require DOCSIS 3 on their networks and have for more than a couple of years, therefore you are not able to improve your performance with any one brand of DOCSIS3 modem, modems are pass through bridged devices, gateways and do not inhibit speed or performance in any way.
    Add to this... do not buy modem / router combos! Do not buy anything that is combo. Remember the old TV / VHS or DVD combos. VCR craps out... no longer usable. Just a TV.
    With modem combos, router goes out, replace the whole thing. No internet. Modem goes out.. same thing replace the whole thing. Modems rarely go down, however WIFI routers do it quite a bit. Wireless routers have several features, non the least the routing capability. But Wireless, that involves different components all together.. it is a radio receiver / transceiver... gets weak over time and usage..and eventually fails. replace the whole thing.

    Does not make sense False #1: ISP to spy on you? Complete nonsense. Any modem, customer owned or leased, that is connected to an ISP's network can be accessed for troubleshooting issues at least, monitor bandwidth usage and to a larger degree capture data that involves copyright infringement, track down wannabe hackers causing disruption on the network, which is not a hard task for any ID10t out there, child porn etc. etc. etc... pretty much crime!
    So accountability for the network and what goes on is solely the ISP's responsibility, therefore ISP's are required to have access at all times to traffic in and out of all the service points in their network. Like a huge day care center as there are so many ID10t's that have to have their behavior monitored. Buying your own modem in no way, shape or form will keep your ISP from "spying" on you. By the way the ISP owns the network, you get on it you are assigning the right for them to "spy" on you if need be.

  12. Anonymous
    September 15, 2015 at 10:26 pm

    Hello, all.
    Kudos to Mr. Gell for his excellent addendum; much appreciated.
    I bought a refurbished"Motorola" DOCSIS 3. a few years ago, about $40, ATT.
    I used it until June this year, when a lightning strike on a nearby power pole got it.
    My local ISP charges $4.99 / month modem rental, so it paid for itself in the first 8 months,
    then I saved about $140-$150, before the lightning ended it's run.
    All in all, excellent performance, & fantastic savings.
    Remember, your ISP has an infinite cash cow when your rent a modem, instead of owning one.
    Have a GREAT day, Neighbors!

    • Dann Albright
      September 19, 2015 at 3:29 pm

      A lightning strike on a power pole, huh? Bad luck! Did it fry anything else in your house?

      (Good call on refurbished, too; that's a great way to save money.)

  13. Anonymous
    September 15, 2015 at 1:02 am

    Info to add:
    - FiOS and U-Verse are not "cable" providers in the sense that they do not use DOCSIS. This is why a DOCSIS modem will not work. The similar looking device they offer is a router with no modem built in. It does have a MOCA gateway that connects to coax and so it looks like one would expect a cable modem to.
    - While manufacturers publish the speeds their modem is capable of, they also rightly advise to check ISP compatibility for speeds in use. For instance, TWC offers 300 mbps service in some areas, and the SB6141 claims to be capable of up to 343 mbps with its 8 bonded download channels. However the compatibility list linked in the article will clarify that the SB6141 will get capped at 100mbps on their network. The 300 mbps compatible modems listed each feature 16 download channels.
    - It was perhaps implied but not clearly stated in the article that both the Ethernet on the modem, as well as the Ethernet on a connected router (or wired computer) would each need to be Gigabit capable in order to reach speeds over 100mbps. To supply a curious example, the $200 Apple Airport Express features only a 100 mbps Ethernet connection at present.
    - The wireless features offered will also be more important to pay attention to, depending on the subscribed speeds, the features that their other wireless devices actually support, or how future proof one wants their equipment to be. There is enough content on that to fill another article, but there are choices between 2.4GHz band only, or 2.4 plus 5Ghz dual-band, where the 2.4GHz channel can be congested by both neighboring networks as well as other consumer devices like Bluetooth. There are options for the number of MIMO (multi-input/multi-output) channels/antennas which can multiply the maximum speed of the modem, and there will be options for support of wireless-n only, or wireless-ac also. Whereas wireless-n is fairly "new" still, it can still be a bottleneck if subscribed to a fast speed tier, where the wireless-ac can handle it if sufficiently supported by the wireless device being used.

    Hope that helps other readers some also. If I've goofed and got something factually incorrect, please point it out, but I think I've left out anything I wasn't confident of or couldn't verify.

    • Anonymous
      September 15, 2015 at 4:35 pm

      I found @Adrian Gell's to be a highly illuminating reply.

    • Dann Albright
      September 19, 2015 at 3:28 pm

      Thanks for all of this information, Adrian! This is extremely useful, especially about the compatibility specs and how a fast modem might get capped by a provider. There are a lot of factors that go into how much speed you can actually get from your connection, and even more when you buy your own modem. This is all really great stuff, and I really appreciate it!