PROS / This cable modem has a relatively low operating temperature.
CONS / Without a power button, you have to unplug the device to power it down.
VERDICT / The Netgear CM400 is a strong cable modem, with fast upload and download speeds, as well as high internet provider compatibility.
Netgear's CM400 is an all-around good cable modem, but it's not quite the best cable modem on the market. You can expect the CM400 to work with most cable internet providers and give you access to very fast internet speeds. With good performance, high ISP compatibility and a decent design, the CM400 earns our Top Ten Reviews Bronze Award. There are many things this cable modem does right, but also a few categories where it misses the boat.
One of the best things about the CM400 is its high compatibility with various cable internet providers. If you get internet through Comcast, Time Warner Cable, Cox or Charter, you shouldn't have any trouble setting up the CM400. Those are the four largest cable internet providers in the United States. The CM400 is also compatible with three more of the 10 largest providers: Bright House Networks, RCN and Cable One.
With the high internet provider compatibility, you have a good chance of the CM400 working with your current provider. This cable modem should also be a good investment for the future, because it will likely work with your internet provider if you move at some point.
The CM400 has a theoretical maximum download speed of 343 Mbps and download speed of 131 Mbps. Keep in mind that those numbers are theoretical – they don't take into account network overhead, network congestion or other interference. Still, the CM400 should be able to handle the fastest speeds most cable internet providers can give you.
We were happy to see that the CM400 is one of the lowest housing temperatures out of all the internet modems on our lineup. At 87.7 degrees Fahrenheit, this cable modem runs relatively cool. This is good news because it means the CM400 is likely to last longer than other cable modems that run hotter. Generally, heat is not good for electronics and is usually caused by inefficiency. The CM400 is one of the most power efficient modems on our lineup.
DOCSIS (Data Over Cable Service Interface Specification) is the technology through which your cable internet provider speaks to your modem, and vice versa. The CM400 makes use of the latest version, DOCSIS 3.0, in order to provide you with the fast download and upload speeds. Those speeds are thanks to channel bonding, which enables the CM400 to pack many data channels into one download or upload stream. Previous versions of DOCSIS only allowed for one channel at a time, severely restricting speeds.
It's somewhat surprising that many cable modems don't have a power button, and the CM400 follows that trend. In order to power down the device for an extended time, you'll need to unplug it. However, the CM400 does have a reset button. This is useful for when you're troubleshooting problems with your internet connection. You also get a gigabit Ethernet port with the CM400. That ensure this cable modem won't be the bottleneck in your home network.
Help & Support
Netgear provides a one-year warranty with the CM400. This isn't quite as generous as some other manufacturers that offer two-year warranties, but it really isn't a big deal. In general, if your cable modem works properly for the first two weeks, it should work reliably for the next several years. These are relatively simple devices, and they usually work 100 percent or not at all. If you find that your modem is restarting itself constantly, then it's probably defective and you should try to return it.
While the Netgear CM400 may not be the very best cable modem on our lineup, it has plenty to offer. It boasts high cable internet provider compatibility and has excellent performance. Unfortunately, the CM400 does not have a power button to help you save money on your electric bill, but you can always just unplug the device. The CM400 is a great cable modem that will work well for most people.