Motorola MB7621 Review

We tested and researched ten of the best cable modems, all of which are less expensive than a year’s worth of rental fees from your ISP.

Top Ten Reviews Verdict

The Motorola MB7621 is a great cable modem that’s easy to set up, supports fast speeds and costs less than renting a modem from your ISP.


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    It’s rated for speeds up to 650 Mbps, and it has an easy-to-use power button.


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    It isn’t the most attractive or compact modem.

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We tested and researched ten of the best cable modems, all of which are less expensive than a year’s worth of rental fees from your ISP. The Motorola MB7621 stood out for its combination of robust performance, exemplary ease of use features and great price. With 24 upstream and eight downstream channels, the MB7621 can easily handle internet speeds up to 650 Mbps. The two-year warranty ensures that it’s lifespan is long enough to save a significant amount of money over renting your home networking equipment.


We hooked the MB7621 up to our network using Comcast Xfinity's 400 Mbps speed plan and ran four simultaneous bandwidth-hogging applications to see how the modem would hold up under a bit of stress. The Motorola modem easily managed streaming Netflix at 4K resolution and downloading three large game files on three different systems (XBox One, PS4 Pro and a gaming PC). This performance was typical in our tests, as every modem we tested passed our testing, but the Motorola's 24 x 8 bonded channels make it a particularly good choice if you subscribe to an internet package with advertised speeds of 300 Mbps up to 650 Mbps. Though its maximum theoretical speeds exceed this, modems very rarely perform at max capacity.

If you have slower speeds, the MB7621 still works well and gives you room to upgrade in the future without replacing your modem. It is up to current DOCSIS (Data Over Cable Service Interface Specification) 3.0 standards and is backwards compatible with DOCSIS 2.0 and 1.1 services.


Because the modems we tested all met our expectations and performed up to their advertised capacities, ease-of-use and other features weighed heavily on our rankings. The Motorola MB7621 has an attention to detail that made it more convenient to use than many other products. One main feature that stood out was its power button. This may seem small, but most modems plug in to turn on, and are only turned off when unplugged, which is a cumbersome process, depending on where you have your home networking equipment set up. The modem also comes with a wrench to tighten the coaxial cable connection and a hook-and-loop strap, both of which reflect a conscientiousness toward common issues that can occur in the setup process.

The MB7621 also includes a helpful set of instructions and a powerful online user interface that offers a range of advanced options as well as the basics, such as resetting the modem and getting the device's information.

Build Quality

Though not the most attractive device, the MB7621's exterior is practical and utilitarian. It won't look out of place in any networking setup. Its sides and top are well-ventilated to protect the device against overheating. It's also protected against lightning and power surges. It isn't quite as compact as the Motorola MB7420, but it shouldn't take too much shelf space as long as its placed correctly. Because the modem needs to be well-ventilated to operate correctly, avoid setting it on its side, as it may overheat.


The Motorola MB7621 is the best modem we tested. Its easily performed up to its advertised speeds when tested with several applications running at the same time, and it’s compatible with most major cable internet providers. It’s also easier to use than other products we tested, so we recommend it for your home network. Of course, check with your ISP to make sure the MB7621 is supported before buying.

Rebecca Armstrong

Rebecca has been writing about technology since 2015. She specializes in smartphones, phone plans, DNA tests and home networking equipment. She has a bachelors degree in creative writing and English literature from the University of Evansville. Rebecca currently works as the co-founder of All Times Are Local, a foster care organization.