Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed review – how to fix issues?


The MB8600 provides high-speed Internet for a computer, router, HDTV, game station, or streaming media device. Active Queue Management significantly reduces Internet latency on both DOCSIS 3.1 and 3.0 services, resulting in faster page loads for all Web traffic and enhanced interactive applications like online gaming and video conferencing. A broadcom chipset provides advanced security from denial-of service attacks. Is it worth buying for you? Get details in Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed review.

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Pros & Cons


  1. High internet speeds
  2. Ideal for Comcast Xfinity, Cox, Spectrum, and many more
  3. Works with any router 
  4. DOCSIS 3.1 compatible
  5. AQM is exceptionally useful


  1. Only 1 Ethernet port
  2. Hard to reach 6Gbps speed limit
  3. Expensive deal

Specifications – Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed

  • Includes: Ethernet Cable, AC Power Adapter, Quick Start Guide
  • Number of Ethernet Ports: 1
  • Dimensions (Overall): 7.88 Inches (H) x 2.25 Inches (W) x 7.25 Inches (D)
  • Weight: 1.1 Pounds
  • Wireless Frequency/Band: No Frequency/Band
  • Wireless Technology: No wireless technology
  • Electronics Features: Gigabit Ethernet
  • Connectivity: RJ-45 (Ethernet)
  • Battery: No Battery Used

Key feature – Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed

  • Super Fast DOCSIS 3.1 with fallback to 32×8 DOCSIS 3.0
  • Downstream speeds up to 3.8 Gbps when supported by your cable service speed and a router that can bond Ethernet ports
  • Up to 1 Gbps upstream speeds
  • Supports the fastest available cable modem services, downloading 46 times faster than DOCSIS 2.0.
  • Active Queue Management (AQM) significantly reduces Internet latency. AQM results in faster page loads for all Web traffic and greatly enhances interactive applications like online gaming and video conferencing.
  • One open and 3 masked 10/100/1000 Gigabit Ethernet (GigE) LAN ports allow connection of any SINGLE device with an Ethernet port including a router, Windows/Mac computer, HDTV, game station. The multiple Ethernet ports are not for connecting multiple devices; they allow connection to a router that can bond more than one Ethernet port to achieve speeds over 1Gbps when supported by your cable service.
  • Includes Broadcom Full-Band Capture digital tuner to enhance speed and save energy.
  • IPv6 next generation Internet addressing support
  • Works with any router, Windows® or Mac® computer, HDTV, or game station that has an Ethernet port
  • Multi Processor Technology with ARM based Application Processor
  • Works with DOCSIS 3.1, 3.0, 2.0, and 1.1 service
  • Future proof, including DOCSIS 3.1, DOCSIS 3.0, 4 Ethernet ports, port bonding, and more

Compare Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed vs Motorola MB7621

Product Type (This table only includes cable modems with NO built-in WiFi router)24×8 Cable ModemDOCSIS 3.1 plus 32×8 3.0 Cable Modem
DOCSIS Channel Bonding24×8 DOCSIS 3.0DOCSIS 3.1 plus 32×8 DOCSIS 3.0
Certified for These Cable Internet Services. Typically Works with Many Others.Comcast Xfinity, Cox, Spectrum, Suddenlink, Sparklight (CableOne)Comcast Xfinity, Cox
Recommended by Comcast Xfinity for Internet Service This Speed Tier or Below600 Mbps1000 Mbps
Maximum Internet Download Speed (Actual speeds are lower)1000+ Mbps6000 Mbps
Built-in WiFi RouterNoNo
Built-in Telephone PortNoNo
Works With Any WiFi Router That Has an Ethernet WAN port
2.5G Ethernet Port

Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed review


The dimensions of this Motorola MB8600 DOCSIS 3.1 cable modem are 7 7/8” tall x 2 1/4” wide x 7 1/4” deep, the vertical design helps a lot to save the desk area and gives it a modern, stylish vibe.


MB8600’s modem comes with four ethernet ports and a single WAN port. The coaxial cable is plugged inside this WAN Port whereas the ethernet port is used for connecting the device with the modem. There are four ethernet ports but you can connect only a single device at a time. This device also works in the same way as that DOCSIS 3.0 modem works.

However, the company decided to modify this modem and brought into market the newer version with just 1 port with the capacity of 10/100/1000 Gigabit Ethernet LAN port.

LED indicator

This is enhanced by the front glossy section, on which reside five LED lights, with the role of showing the status of the Power (green means the device is powered on), Downstream (if the LED is blinking a green colour, then, the modem is scanning for a downstream channel, while, if it is solid green, then it is connected to a channel; if the LED is blinking blue, then the modem is negotiating bonded channels and, if it is solid blue, then, it is connected to two or more channels


A powerful Broadcom BCM3390ZRKFSBG chipset that comes with 512 MB of RAM and 128 MB of storage memory. 


The MB8600 is too fast for a single gigabit Ethernet port. You actually have to use four of them if you want to max out the modems 3.8 Gbps maximum downstream bandwidth. Currently, you’re limited to the 1 Gbps maximum internet speed offered by cable providers. This is the theoretical maximum bandwidth that DOCSIS 3.0 can offer, so if you’re in a 3.0 area you won’t see speeds improve for a little while.

Signal strength

Cable internet is divided up into 32 channels. A modem that caps out at around 500 Mbps might only have access to the first 16 channels. Since only ultra-high speed modems use the upper channels, these are emptier, and typically have a cleaner signal.

Even if your ISP only provides access to 8 channels, they don’t restrict what channels you can use. This modem receives the entire DOCSIS band, and can pick and choose channels that are the cleanest. If you’re struggling to get the advertised bandwidth due to a crowded network, or aging lines, this modem could be the answer.


Motorola MB8600 is compatible with all the leading Internet Service Providers(ISPs) such as Cox, Spectrum, Comcast Xfinity, etc. Looking at the cut-throat competition in the market, making a modem compatible with all primary ISPs is quite a feat. Motorola is known to have played a crucial part in the development of DOCSIS, giving us all the more reasons for advocating the benefits of Motorola MB8600.

Motorola MB8600

It supports both DOCSIS 3.1 and DOCSIS 3.0. In many ways, this makes it the ultimate future-proof device. You can buy it now, even if your ISP hasn’t updated. When they do update, you’ll be first in line for the new packages available.

The modem is already certified for Comcast XFINITY, and you can use it with any package they offer. They also let you change your modem online. Just log in, and enter the new serial number – no need to call in!

Setup and activation

Regardless of which modem you choose, you’ll need to activate it once you get it. Each ISP has a different activation process, but you’ll need to either call the company or visit a URL to activate your modem. Here’s how to activate your new modem on ComcastSpectrumCoxSuddenlink, and Sparklight/Cable One. You’ll need to call WOW’s customer service line to activate your modem with that ISP.

I tried the Motorola MB8600 (via a few units) with a couple of Comcast Xfinity accounts, and the setup process was straight forward. You can find detail in this post, but here is the simple breakdown:

  1. Connect the modem securely to the service cable.
  2. Turn it on and wait for the signal light (2nd from bottom) to turn on solid green.
  3. Connect a computer to the modem’s LAN to a computer. Alternatively, you can also connect this port to a WAN port of a router, then connect the computer to the router (either via Wi-Fi or a network cable.)

And you’re done with the hardware setup. Now it’s time to activate the modem. For this, you can just call the provider and give them its MAC address, located on its underside.

Or, you can do that yourself, which I did. When I launched a web browser on the said computer with an Xfinity account, I got directed to the activation page, where I entered my account information. And voila! Mission accomplished.

(By the way, it’s always a good idea to restart the router after the modem has been activated.)

Most other cable Intenet providers should have a similar self-activation process. But, again, when in doubt, it never hurts to give yours a call.

While generally, there are no user-accessible settings in cable modems, the SM8600 does have a web interface reachable via its default IP address, which is The interface shows its status, logs, and other useful information about the WAN connection.

Modem compatibility list, updated June 2020
Cable modemComcast XfinitySpectrumCoxSuddenlinkSparklight/Cable OneWOWMediacom
Netgear CM600 (24×8)Up to 960 MbpsUp to 400 MbpsUltimate ClassicUp to 500 Mbps1Up to 600 MbpsUp to 600 Mbpsn/a
Motorola MB7621 (24×8)Up to 846 MbpsUp to 400 MbpsUltimate Classicn/aUp to 300 MbpsUp to 600 Mbpsn/a
Netgear CM500 (16×4)Up to 372 MbpsUp to 400 MbpsUltimate ClassicUp to 500 Mbps1Up to 300 MbpsUp to 600 Mbpsn/a
Motorola MB8600 (DOCSIS 3.1)Up to 1,000 MbpsUp to 400 MbpsGigablastn/aUp to 1,000 MbpsUp to 1,000 MbpsUp to 1,000 Mbps
Arris SURFboard SB8200 (DOCSIS 3.1)Up to 1,000 Mbpsn/aGigablastn/aUp to 1,000 MbpsUp to 1,000 MbpsUp to 1,000 Mbps
Netgear CM1000 (DOCSIS 3.1)Up to 1,000 MbpsUp to 1,000 MbpsGigablastn/aUp to 1,000 MbpsUp to 1,000 MbpsUp to 1,000 Mbps
Netgear CM1100 (DOCSIS 3.1)Up to 1,000 MbpsUp to 1,000 MbpsGigablastn/aUp to 1,000 MbpsUp to 1,000 MbpsUp to 1,000 Mbps
Netgear CM1200 (DOCSIS 3.1)Up to 1,000 MbpsUp to 1,000 MbpsGigablastn/aUp to 1,000 MbpsUp to 1,000 Mbpsn/a

1 Suddenlink told us that all DOCSIS 3.0 modems will work with the company’s service, but you should call Suddenlink to verify compatibility before purchasing.

Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed performance review

I tested the Motorola MB8600 (via a few units) over two weeks with a couple of different Xfinity accounts, and the modem proved to be fast and reliable.

First of all, in the San Francisco Bay Area it consistently deliver speeds faster than that of the plan for those with a sub-Gigabit connection.

Specifically, for an account with a 400Mbps download speed, I experienced up to 460Mbps. And with a 600Mbps plan, I was able to get faster than 700Mbps. The upload speed was never faster than some 20Mbps, which is normal for all cable connections.

On the other hand, when tested with a Gigabit cable plan, the modem capped at just around 960Mbps. That was likely because a Gigabit connection generally caps at around 950Mbps after overhead.

Needless to say, your mileage will vary. Cable broadband connections tend to vary from one area to another. But it’s safe to say the Motorola MB8600 sure can deliver Gigabit-class broadband.

Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed customer review

OMG! What this did for my downspeed is incredible!

Only ordered this DOCSIS 3.1 modem to create backup device out of my older DOCSIS 3.0 modem. I realized that during this COVID-19 pandemic I should have a backup of every device needed to keep us on the Internet due to work-from-home, kid’s school-from-home, Tele-Health doctor appts, grocery ordering, general online shopping, etc. We’re very Internet dependent even during regular times. Once it was installed and everything rebooted, my download speed shot up from my normal 110-126 Mbps all the way up to speeds way in excess of 500 Mbps. Just a moment a go I tested my speed and it was 578 Mbps. See my photo. On my Comcast bill you can see that I’m paying for Comcast’s Extreme 105 Mbps Internet package. See my photo. Overall, I’m blown away by what this Motorola 32 x 8 DOCSIS 3.1 Cable Modem did for my download speed! Couldn’t be happier with it.

By Steve62305 at Best Buy

Alternate – Motorola MB8600 DOCSIS 3.1 cable modem 6 GBPS max speed

Netgear CM500

America’s average internet speeds measure around 100 Mbps, ranging from the low 20s to figures approaching 97 Mbps, depending on which survey you pick. If your plan is in that range and you don’t intend to upgrade beyond 300 Mbps anytime soon, we recommend the Netgear CM500. The CM500 matches the ISP compatibility of the pricier CM600, but its maximum download and upload speeds are lower (300 Mbps on the CM500 versus 600 Mbps on the CM600, though Suddenlink certifies it for 500 Mbps speeds). The CM500 has a good reputation for reliability, but like the CM600 it comes with only a one-year warranty.

Motorola MB7621 

The Motorola MB7621 is reliable, supports the fastest internet speeds available to the vast majority of Americans, and offers compatibility with just about every non-gigabit plan from every cable internet service provider in the US—including Comcast Xfinity, Spectrum (formerly Time Warner, Charter, and Bright House), Cox, Suddenlink, Sparklight/Cable One, and WOW—which gives you flexibility if you move or switch ISPs. The MB7621 works well for plans up to 600 megabits per second, because it’s a DOCSIS 3.0 modem that can handle 24 downstream channels and eight upstream channels. It also includes a two-year warranty.

Editor’s recommendations

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