Motorola MB8611 DOCSIS 3.1 Multi-Gig Cable Modem | Pairs with Any WiFi Router | Approved for Comcast Xfinity, Cox Gigablast, Spectrum | 2.5 Gbps Port | 2500 Mbps Max Internet Speeds

I ordered this motorola modem to replace an arris surfboard 6183 that i had had for 5 or 6 years. I was having to reboot the surfboard a few times a week when my download speeds would drop to 20 or 30 (i should get over 300). Learned that was an issue with the surfboard. Motorola is made by the same company but doesn’t have puma chip issues (latency and jitters) that the arris does.
So, setup (and i am not a techie….i’m a senior who learns by her mistakes) was easy enough. The ethernet cable that comes with the modem is very short. That is ok if your router is very close to your modem. In my case, my router is up high on a shelf across the room from the modem, and i need a big step stool to reach it. I have a very very long ethernet chord and needed to make sure it would work (i don’t interchange things like that without asking). Forget reaching anyone in motorola customer service by phone. Email they say they will answer within two days….i finally got through on chat support. The guy answered right away. Yep, it will work. Same category 5. I turned the modem on and everything connected except bottom lan light kept blinking green. I hadn’t closed my chat with motorola so i asked that question….the man answered that was normal. Checked my speed. Where i had normally gotten around 325-350mbps, it was 25. Not good. Motorola guy was still around and he said it was an xfinity problem – they must not have configured it right when they activated. Eeeeee. I called and you don’t want to go through that robot voice hell if you don’t have to with xfinity. The robot restarted the modem. Said call back in 10 minutes. I did. Robot insisted on restarting the modem again. We went through this 3 times before i got my call put through to an agent….but another robot said my wait time was over 2 hours. I put the phone to the side and managed to be 53 in line on a chat with xfinity. I will not go into detail but that was a waste…the chat guy never understood the problem….phone lady finally answered after only 45 minutes. No issues with the modem she says…let’s reboot your router. Stupid me stupid me. I should have thought of that. Reboot router so he recognizes the new kid on the block. I knew that…my brain was in a fog i guess. Would have saved me about 2 hours of aggravation. Rebooted. My speed was then 365 mbps. It has held steady at more than what i pay for (xfinity is good about that).
So, buy this modem. Make sure your router is new enough to support it (i have a netgear nighthawk ac1900 that is apparently the minimum you can use but it is an amazing router). Make sure you have a compatible ethernet cable (being category 5 seems to be the key and it is written on all cables) if you need it longer than about 6 ft. (or maybe 5 ft – it is short). I’m hoping this modem will last 5 years or so. I am a happy old lady. My hubs is happy because he can stream the golf channel without buffering. My alexas work in every room, my light bulbs and doorbell are nicely connected and all is right with the world (or at least in my home)

This was purchased as an upgrade to my arris surfboard ac1750 docsis 3.0 cable modem router (sbg6782).

Being nearly 7 years old and reaching the design bandwidth capacity of the modem, i wanted one that could allow future growth as the minimum speed for internet service has gradually been increasing.

My original unit still works flawlessly, but did not have a strong wifi signal that reached outside my apartment.

After a bit of research i determined that buying a separate modem and wifi router was the way to go.

Had this modem for nearly a year and has worked without a single issue since the day it was first hooked up.

I can say however that my foray into buying a wifi router did not go smoothly the first go round, my first unit turned into a ‘brick’ within less than 90 days (major chip flaw problems with that model). So i settled on the netgear nighthawk ax6 6-stream ax4300 wifi 6 router (rax45-100nas).

The latter wifi router took a bit of work to set up, so the average consumer here will likely get frustrated trying to hook that particular model up. However it has amazing signal strength in and outside my apartment, and my wifi streaming has never been better, all without the need for a mesh network.

Highly recommended… Just be sure to read carefully the product features, do your research and know exactly what you are buying beforehand. Too many reviews of people complaining that didn’t know this is that feature wasn’t on the product they bought…. Why… Cause they didn’t bother to read.

Received the motorola docsis 3.1 cable modem on-time from amazon. Up and running within 15 minutes, no call to comcast.

Motorola ultra fast docsis 3.1 cable modem, model mb8600, plus 32×8 docsis 3.0, certified by comcast xfinity

paper instructions were in the box and also online. No firmware available for prior update. I had previously confirmed that this device is acceptable to comcast. Before buying any network device, always check that your isp supports the device you plan to buy. Unacceptable for us to rate an item poorly if its is not compatible with your stuff…

I replaced a cisco – linksys model dpc3008 docsis 3.0 cable modem purchased thru amazon for $90 exactly five years ago. It has never failed. I would have paid comcast say $10 / month to lease their inferior modem for the last 60 months, using the roughly $510 savings to enjoy comcast ‘blast’ speeds not supported by their leased modem. I viewed this purchase as another future-proof, leading edge decision to replace a 5-year old $90 device. I did not expect a speed increase. Here is why.

If i log into my comcast account and search for upgrades for my internet service, there is only a fiber option. I am maxed out at a supported wire speed of ‘150 mbps’. I attained that with the 5-year old docsis 3.0 device. So, comcast does not yet offer docsis 3.1 service here; and, they will not reveal that to customers. I searched for a couple of hours for that revelation. The new mb8600 has a connect led the turns blue with a 3.1 connection else stays green to confirm 3.0 per the instructions. Mine is green now. So, ‘no’, comcast has not brought docsis 3.1 to my area.

Follow the instructions. They work. I suggest however that you perform a broadband speed test prior to switching out your old cable modem. I also suggest you have your comcast account number from a bill and ensure your comcast account has your current phone number. Not clearly said; but, i also suggest that you eliminate your network’s switches / routers / wi-fi and simply ethernet connect to any one of the four gigabit ethernet ports on the back of the mb8600. I used port one.

The mb8600 synced up with comcast quickly (according to the lights); but, i could not obtain an internet connection. I’m guessing windows 10 pro simply was trying to protect me from a new intrusion. This is not a windows 10 / microsoft edge issue. Solution: delete all network settings, reboot and there it was, comcast activate. Enter your data and your mb8600 will reset. Once completed, i was online within 15 minutes. But, the speeds i had before were faster than now. Guess that my firmware had not yet been updated by comcast.

The label on the bottom of the mb8600 has an ip address, user name and password. I logged in and saw that the modem had provisioned to docsis 3.0 with only one channel down and three channels up, far below its capacity in 3.0. You resolve this by pressing in the reset button on the back of the mb8600 for several seconds till the lights flash. After, i now have 24 channels down and three channels up. I then retested my speeds to confirm that i was exceeding the comcast extreme 150 service level i am paying for: 180 mbps down / 24 up. That is a roughly 10% improvement still on docsis 3.0. Again, comcast here does not seem to support any faster wired speed than 150 mbps, and deeper level of docsis 3.0 than 24×3 and no docsis 3.1, now, no docsis 3.0 32×4 either. I can hope but aol is perceived as ‘high tech’ here…

I hate contacting comcast customer service since i always feel as if i am training them. I may invest the day it will likely take to get comcast to remotely re-provision my interface with them. Maybe not.

Satisfied that i was connected as well as i could, i then moved on to reconnect my router for its wi-fi and more importantly for its added trend micro security not offered by the mb8600 since it is not a router, its a cable modem. My configuration is mb8600 to an asus router with 4 gigabit ports and wi-fi ac2400. One wired port feeds a dumb gigabit switch supporting five devices. A second wired port supports my microsoft book. I’m a retired it guy so i avoid wireless connections excepting my cell.

Yes, i have my cable modem, router and pc powered thru an uninterruptable power supply. The mb8600 documentation states that its power supply is resistant to power surges. We have afternoon storms all summer. Its fun to continue surfing while neighbors are dark; yet, my comcast and directv both work fine with a ups power supply. Good that motorola upgraded to some surge protection; but, i want that and sine wave continuous power. For your consideration….

The mb8600 has been connected for roughly six hours. It is barely warm and only at its top. Off to a good start.

Update jul2018: the mb8600 is still running like a champ. No issues. Comcast finally has some competition from century link with its fiber optic gigabit offering wired into my neighborhood just days before hurricane irma. I signed up for it since its cost was just a minor bump for gigabit from 150 mbps. A few months ago, the green docsis icon turned from green to blue indicating that comcast had turned on version 3.1 but; i was provisioned for 150 mbps and did not see a speed jump. Nine months later, still no century link offer.

Regardless, i opted to move to a different home. Unfortunately an older neighborhood with no century link fiber optic. But comcast does offer gigabit speed at a higher price. Comcast’s cables here are 30 to 40 years old unfortunately.

I’ve been with comcast for well more than 8 years. This was the first move / install that was completed correctly the first time. The tech clocked 960 mbps at the mb8600 down. My pc sees less speed (580 to 870 down) with a reliable 40 mbps up. The mb8600 performs as advertised. All 32 downstream channels and 4 upstream channels are locked.

Warning: this is a long review, but i may have some angles on this others don’t 🙂

wow. I really like this modem. This is a barebones rock solid dead simple workhorse.

It’s got a plug for the cable and one ethernet (rj-45) port out and i think an on/off switch.
That’s it. It makes a connection. And hasn’t failed since i got it a month or so ago.

All i had to do was call my isp and give them the mac address (on the sticker on the device)
and they updated their tables and that was it. Turn it on. It goes through the startup cycle. Takes a few minutes to connect like they all do and that’s it. Set it and forget it.

What prompted me to get it, is i don’t like having to rent the modem from the isp @ $10.00/mo forever. This literally pays for itself in 16 months, and most people will have their internet connection for many times that long, and time flies. So it’s a good investment.

It doesn’t have phone connection like the isp’s modem did. So i called the company/provider that owns copper phone lines in the area and ordered landline service. I’m a nerd/techie and don’t care what people say about landlines being for old fogeys, it’s like having a backup generator … I know i can use that landline if the power goes out or if the cell tower gets overwhelmed (too many calls or cell traffic at once), or there’s radio interference in the area. Technically cable phone is a ‘land line’ (hardwired cable connection to provider) and the battery backup in the modem (which the isp charges more for), could give you emergency phone service in an outage, but a cable phone connection can (and does) fail for more reasons than copper wire phone service does. (those copper wire connections are called pots – which stands for plain old telephone service), and copper wire phones are the most reliable.

Having a separate modem from a router is optima for a few of reasons… Generally hybrid units of anything do everything okay, but nothing optimally (for example combination modem-router units like my isp rents out). Better to keep the modem separate from the router. Then you can swap either out independently to upgrade as needed, disrupting less of your own network configuration doing so, and also help avoid a single point of failure. Plus, you might be able to score a router in a pinch on shorter notice than a cable modem if the router is the component that fails. Then you can choose the router you actually like, for whatever reason, and don’t have to settle for whatever bundling du jour your isp decides is right for you (even if it isn’t).

That gets me to the other point. What did the isp decide was right for me (but wasn’t)?

For awhile my isp modem connection was dropping briefly in the middle of the morning. My computer came back up connected to the isp’s ‘general public’ wi-fi connection to their router which did not work for me and i’d have to keep manually switching back to my own internal wi-fi lan (network). That was not only inconvenient but it forced me to investigate was was going on there.

I learned my isp gives lets passersby connect to their rental-modem’s wi-fi signal, without giving me any way to disable that service! That really pissed me off to learn. The idea is that people driving around who have accounts with the provider can get internet access around the neighborhoods. If i was a passerby, that could really help me, so at first glance maybe ‘why not, be a good samaritan’.

But wait! There may be more too it than that.

Besides the fact that i don’t like it (for good reason), they give me no control over that ‘feature’!
And i see some downsides. What’s good for the isp isn’t necessarily optimal for me.

What i don’t like about that ‘service’ is that one or more people could sit outside and suck down bandwidth (e.g. Slow my connection down), unbeknownst to me. It also might cause the unit to use more energy and put out a stronger wi-fi signal than it needs to. Which health conscious people are well advised to be aware of. Wi-fi is radiation. Not strong and may not ruin your life, but it is a stressor at a cellular level, this is known. And strong signals, persistent signals and people who are more sensitive or have immunity issues can be more vulnerable (headaches, sleep disruption, or worse). But i like wi-fi so i settle for whatever unknown health consequences i may not be aware of.

Also it makes me wonder if a hacker might be able to use it as an additional point of access to my home network.

I also wonder if it’s 100% clear to law enforcement at first glance who might be visiting sites or doing something nefarious from the connection point. Might it look like the owner is doing something that a passerby did (and even if they can sort it out later, what if it takes awhile to figure out and they make a bad assumption?)

anyway, i don’t have that problem with this modem and i’m just much happier with it all the way around.

Plus it’s blazingly fast.

The only issues i have had with this item is when comcast tells me there are service outages in my area. Every other time it just works tirelessly for about the past year and change.

I have it on a timer to go off every night and on every morning and that has worked extremely well for me. Hopefully it adds to the product longevity, if even a little bit.

The xfiniity compatible modem was super easy to set-up following the quick start guide included in the box. Word of advice for comcast / xfinity subscribers — when stepping through the set-up wizard, selecting the option to text an activation code is a joke — the code is only good for 15 minutes but i didn’t receive the text until 30 minutes had passed; just stick with your xfinity account name for the activation and provisioning.

Xfinity upgraded to docsis 3.1, and, while my own 6 year old trusty motorola surfboard sb6580 was working fine, xfinity found every reason to pester me about an upgrade and how much i’m missing not having a 3.1 modem lease an upgrade. I prefer to own my own modem, so, after perusing compatible modems for my region on xfinity’s approved device page, i narrowed my choices to the arris surfboard sb8200, netgear cm1000, and, this, the motorola mb8600. All three are comparable at 1001 mbps, 32 down x 8 up docsis channels, and docsis 3.1.

All the cool kids love the arris — especially after they ditched the very problematic intel puma chipset and went with the broadcom’s offering — and for very good reasons, it has great hardware specs. Sporting 3gb of ram, 128mb /16 of nand flash memory it’s a tasty treat. And, were it not a horrific white box that clashes with everything in my apartment, i’d happily have purchased it.

Vanity, thy name be monkey rat, i know.

I’ve never had a lot of love for netgear, and, i found its hardware lacking — 128 mb of flash memory and 256 mb of ram. Ultimately not a huge game changer, with current theoretical home speeds at 1gb, but one would expect something a tad more, well, more from a name like netgear. While its feature rich — which, is saying something for a cable modem — i really saw no reason to down this path.

That clashing white arris was looking tastier at this point.

Then i compared the mb8600 to both and found a happy place. 512 mb of ram and 128 mb of nan — a buck cheaper than the netgear with a doubling of the ram, and while not as expensive — marginally — than the arris, and certainly lacking a bit in the hardware department, but i paid more for future ability to bond upwards of 4 separate lines. However, the lacp technology requires a higher end router, and faster than a gig speed isn’t necessarily right around the corner, but, this device positioned nicely for a future with a potential of 4gb.

Word of caution — it’s a big device. If you’re familiar with the older surfboards, this is easily double the size in height and does not come with any sort of mounting option. However, it has great ventilation thanks to a well aired grid pattern on the side.

So, how does it work? My internet plan is the blast! 150 mbps (stop laughing) — and i assure you, i’ve never seen that even in the dead of night — wired speeds show an increase on speedtest.net but it’s not really all that noticeable, whether plugged in directly to the cable modem or my asus rt-ac86u router, notebook and desktop performance were negligible. However, wireless performance for my nvidia shield k1 tablet and google pixel 2 phone were significantly improved – i found this a little odd as they’re still going through a router, but, i can’t argue with results.

I keep forgetting the mb8600 has a baked in spectrum analyzer utility i need to check out — i’ll add an update when i do.

Ultimately, i like it — i play everquest (the original) and noted better response times, but again, the ms aren’t earth shaking or setting the sky afire. Stream the occasional movie, and really i don’t have any complaints, and can only praise the device for its eye-popping wi-fi boost, for which i have no good explanation.

I may change out my cat5e for cat6 and upgrade my router next — hopefully wringing a couple more mbps out. But, really, i think it’s time to call xfinity and have to do some line tests. I will provide updates on that as well.

I recently cut the cord and decided to buy one of these. I was paying comcast almost $300 a month for cable that i don’t watch. Now i just stream what i want to see, and all i pay for is internet. This modem works flawlessly, and it was very easy to set up. I paired it with a linksys wifi 6 system. I definitely recommend buying one of these instead of paying monthly rental fees to a cable company.

Pricy, but worth it. Motorola is the go to brand for high quality. This modem delivers, but remember keep in mind you have to use a router in order to use multiple devices in your home. I got the motorola ac2600 4×4 wifi smart router. Installation of both devices was very easy. Literally, plug and play. However, you will most likely have to deal with your internet service provider in order to register your modem with their service and allow the modem to receive their signal. That was the most painful process. Everything else worked flawlessly. After buying and installing both the modem and router, i upgraded my roku device to the roku ultra hd/4k streaming device with voice activated remote. I’m very pleased with the results i got. See my review for the roku ultra below:

for about three years, i was using the same roku device that was provided free with my sling subscription. It was frustrating to watch a movie only for it to stop and start buffering. It was frustrating to try and watch youtube content only to crash during the ‘loading’ period or stop in the middle due to buffering issues.

After researching and troubleshooting i came up with the following fixes that have resulted in awesome streaming, seamless channel surfing and no buffering once any channel is loaded (within 5 seconds or so).

First, you need to run a speed test of your current internet. You should get results like 400mbps on a higher end laptop (i.e., macbook pro). If you get anything less, you need to up your internet service provider download speed. If you have multiple devices, i recommend at least 600mbps. Ideal would be 1000mbps. Next you need to make sure your modem can handle the speed. I got a motorola mb8600 modem. This modem will handle speeds in the gigabit range. Hold on, that’s not all. With this modem you need to get a router that can continue to support the new speed and the internet service that you are working with. I bought a motorola ac2600 4×4 wifi smart router. This router will increase coverage to your home and will seamlessly support the internet speed and connectivity of the motorola modem.

All three of these devices compliment each other and will help you dramatically improve your video streaming ability. Please keep in mind that if your internet service isn’t high enough, you will not get much of an increase in performance. You have to look at the entire system in your home.

1. The internet service that you are paying for monthly. This is critical. It has to be high enough (600-1000mbps).
2. A good modem. Your modem is the device that takes the internet signal coming from your service (i.e., xfinity, verizon). I recommend you make sure your modem can handle speeds in the gigabit range. This should be good for about 3-5yrs.
3. A good compatible router. The router takes the signal from the modem and splits it so that multiple devices can use the internet signal coming into your home. Note- there are cable modems out there that are combination modem/routers. If you are on a budget they will work. However, i have found that my new combination of separate modem and router has improved my internet performance tremendously.

Lastly, if you are on a budget and can’t afford all the upgrades, then getting this roku device will just be a waste of money. This roku device is a high-end streaming device that will only perform at it’s best if you have all the other devices in place that can provide the clean and fast internet signal it needs. I did a complete overhaul of my home system and can’t be more pleased with the results. I replaced each component that i’ve described in stages just to see if each device really made a difference (a noticeable difference). I’m happy to report that each stage made a big difference.

I wasn’t sure if it would make much of a difference, but my internet bandwidth went from around 220mbs to approximately 330mbs. My old modem was a zoom brand but only docsis 3.0. So far, this modem has been working great. One this i would suggest for anyone paying for 100mbs or more of internet bandwidth, is to make sure the cable you’re using is cat 5e or better. Regular cat 5 cable can limit you to only 100mbs.

I’ve been running an arris sb6121 cable modem for about eight years now, but have been having some outages recently, in which the modem appeared to be at least partly responsible. In addition, the sb6121 is getting old and can support only four download channels, limiting its ability to use higher service speeds now available. My isp advised that i upgrade, and given that my isp is rolling out docsis 3.1 starting in november, i decided it made sense to go with a docsis 3.1 modem.

Right now, that narrows the choice pretty much to three devices: the netgear cm1000; the arris sb8200; and this modem, the motorola mb8600.

The cable technician who just replaced my line advised against the netgear due to having seen a lot of reliability issues with netgear cable modems, but had no preference between the arris and the motorola. Since their specs are almost identical, but the sb6121 has had some firmware download issues and the motorola is $30 cheaper than the arris (and has a two-year warranty), i went with the motorola. The motorola, unlike most other cable modems, also has an actual physical power switch, so should you need to power-cycle it you can do so without unpligging it.

Both this modem and the arris have two gigabit-ethernet ports. Yes, i know, you can only see one in the photos. And you’ll only be able to see one when you take it out of the box. That’s because the second port is hidden under the yellow adhesive film on the back panel.

There is a reason for this. That second port is not for plugging in a second device, and you cannot use it for that purpose. Don’t try. The second port is there so that if your router is capable of it, you can connect both ports to your router and bond the two gigabit channels together into a single 2-gigabit channel. Your router must support this, your isp must enable the second port,1 and it’s up to you to configure the router correctly for port bonding/trunking. Of course, this is only relevant if your isp offers data rates over 1gb/s *and* your router can support that anyway. If you’re a residential user it’s unlikely that both of those are true.

When you’re switching to a new modem, you’ll need to call your isp and you’ll need the mac address from the sticker on the bottom of the modem. You will need to power your router off and wait for the modem to initialize fully the first time before you turn it back on. Expect that first-time initialization to take several minutes. Once the modem is online, bring your router back up and you should be good to go.

As soon as it’s up, point a web browser at 192.168.100.1, log in to the modem using the default password on the sticker on the bottom of the modem, click advanced, click security, and change the admin username and password. Both allow you to use only a-z and 0-9, which is a little weak. But you’re allowed up to 15 characters. Use as many of them as you can to make your new password harder to guess — and no, don’t use your dog’s name, your phone number, or a dictionary word as a password. Make sure you record what you changed it to. Don’t lose it.

What do you get for your money? Well, in addition to docsis 3.1 support, the mb8600 can bond up to 32 downstream and 3 upstream data channels. In my case, with no change in my service cost, my download bandwidth increased from about 46 megabits per second to about 96.5, and my upload speed from about 4.5 megabits per second to 11. Viewed from the perspective of what i was paying for what service tier, this modem will pay for itself in about a month and a half. With eight times as many download channels, it is also much more resistant to noise or other problems on any single channel.

So far, the motorola mb8600 earns a solid two technical technical thug thumbs up. It is a substantial improvement over the arris sb6121 it just replaced.

____
1 well, ok, you *can* enable it yourself in the advanced configuration on the modem. But if you’re messing with advanced configuration settings, you’d better know what you’re doing. If you don’t, you’re on your own.

I do not rent modems from cable companies. Long since figured out better to own it then pay for generally outdated tech. This time it got me a bit. Spectrum in our area has been steadily increasing our cable internet speeds. I was going to blame spectrum for us continually loosing connectivity but i did some hunting and found out our modem was just cooking and could not keep up with the upgraded internet service we were getting and using as we have steadily doubled the number of devices we have using it. Spectrum has more then doubled our speed in the last two years, and we have got at least 2x the devices using our internet now – no small wonder the old modem cut out. Looked up the specs and this one should future proof us for 4 years or more. Easy to hook up, the hard part is waiting on the phone for spectrum to do their end of the hook up. Once you finally get someone on the phone they did very well and now i have screaming fast internet and it does not cut out. Only complaint with the modem itself is the dang bright lights! I wish there was an option to dim them. Great product otherwise.

Did i mention fast? Alright, other than comcast getting the mac wrong, it all works great. My old modem had led light leakage and those diodes were bright. This modem is well assembled, minimal io, making it fast to hook up, and it’s fast! Speed test saw a 10% increase in down stream, up tested just 2% faster, however that was the max upload from my isp. Hoping this is a future proof modem for the long haul. The only thing faster and more channels is 3 times the price and is overkill, unless it’s a campus enterprise. In conclusion,, bring on the fiber optics comcast!

Got the product. Installed it. Worked pretty easily, however within a month it was intermittently cutting out. The cable company’s diagnostic app said the modem was going offline often (several dozen times per day). That makes it hard to maintain a vpn connection for work-from-home. I bought another modem of the same make & model at a local computer super-store and it has worked flawlessly ever since. It might have been damaged in a thunderstorm. No way to tell now.

This modem is great until it doesn’t work. On two occasions in only a few months it’s become unresponsive and spent the day with upstream issues. Nothing seems to resolve it but time. Luckily i can log in through my isp’s public wifi because the motorola is not reliable for wfh.

Trivial to install; i unplugged my xfi modem/router, plugged the coax into this one and powered it on. It was visible in the xfinity app in about 5 minutes and fully functional (at maximum speed) in about 10 minutes. I can’t evaluate the >1gbs performance/ability because i’m at 400mbps but i’m definitely getting that (more like 470).

No wifi signal review because it’s a modem only. I have mine connected to my old google wifi (not even nest) which i’ll probably replace soon.

Minus 1 star because the base is very unstable; with the semi-rigid coax cable screwed into the back, it’s very hard to find a placement where the cable isn’t tipping the modem over. I’d lay it on its side but i’m worried about airflow (it definitely runs warm).

I’ve had problems using the mb7621 docsis 3.0 modem with xfinity’s ‘fast’ internet service, which delivers 300mbps downstream and 10mbps upstream. Initially the performance was as advertised, but over time, or after a reboot, performance would drop to 50mbps downstream and sometimes less than 10mbps downstream, while the upstream performance was maintained.

After some investigation, i found that the problem may be with how comcast handles the ‘extra’ channels not used by my data plan. My plan only needs 16 channels to deliver 300mbps, while the modem supports 24 downstream channels. So comcast only sends internet traffic on 16 of the 24 channels; the last 8 are unused.

It looks to me, though, that the modem sometimes receives ‘other traffic’ on the 8 unused channels. I’ve no idea what this data is, but the modem interprets it as noise or invalid data, and reports millions of errors per minute on these channels. Handling those errors takes processing power, resulting in the performance reduction i see on the data over the 16 ‘real’ channels.

If you look at the two pictures above, one shows no signal on channels 17-24. This is the ‘good case’ where the number of errors seen on those channels is small enough that performance on the other 16 channels is not affected. If you look at the second picture, which shows a snr of ~29 on channels 17-24, the error counts are much higher – this image was taken just a few minutes after restarting the modem – and the throughput performance suffers. That is the ‘bad case’.

So who is to blame – the modem or comcast? I honestly don’t know. But i think comcast should be filtering out data on the unused channels, or configuring the modem to only use 16 channels in their configuration file. It’s possible that the modem is introducing the noise – but it’s strange that it only happens on the unused channels.

I don’t have a solution for this yet, other than to reboot the modem until it comes up into the ‘good’ state. I have had comcast technicians out to the house twice, and the second one made changes that initially seems to ensure the modem booted into the ‘good state’, but the modem reverted to ‘bad state’ behaviour later.

The answer may be to use a modem that only supports as many channels as you need for your plan, so that the modem is not subject to traffic on other channels. Or maybe docsis 3.1 doesn’t have this problem, and a new modem is in order.

I’ll update this review as i try out more solutions.

Wish you could turn off the lights like arris, and wish is was a bit shorter. I found out motorola leased out the tech from arris, so i would rather just buy from them.

It works as one expects but has only one ethernet port so that even in a home office you’ll need an ethernet switch to connect more than one item.
I can’t speak to the wireless signal since i use a tp-link mesh set-up, as much as i hate using wifi.
Set-up via mediacom was quick and easy, so i’d buy it again if the need arose.

It works but it is slower than normal due too the lack of cat5 access ,you have to add a wifi router which chokes it down in speeds ,i’m getting 98 mbps compared to my old 305 mbps modem

So far its a good value for the money