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Modem vs. Router: How They're Different and What They Do

When it's time to set up a home Wi-Fi network, it's important to know exactly what kind of equipment you need. Everything starts with two pieces of gear: a modem that brings internet into your house and a router that directs that internet connection to all the computers, tablets, mobile phones and other connected devices you have on hand. The two devices work together to fill your house with cat videos, Snapchats and all the other things that make the web so wonderful.

Credit: Shutterstock/Casezy idea

(Image credit: Shutterstock/Casezy idea )

Here's a quick rundown of both types of networking gear, including what to look for and why you're usually better off opting for a separate modem and router instead of a hybrid device.

Modems: Your gateway to the internet

To bring the internet into your home, you're going to need a modem.

This is a small device that connects to your internet service provider (ISP) to tap into all that internet goodness. The connection is made via a cable (for cable or fiber internet) or phone line (DSL) from outside your house that plugs into the back of your modem. Your modem shares this connection with a computer or a router via an Ethernet cable.  

Modems aren't one-size-fits-all solutions; the type of modem you'll need depends on the type of internet service you receive. If that's DSL, you'll need a DSL modem. If your ISP offers cable internet, you'll need a cable modem. If you choose fiber, you'll get an optical network terminal (ONT) to translate the fiber-optic light signals into electrical signals that your devices can recognize, and maybe another modem-like device to translate from the ONT.

Arris SURFboard SB6121 cable modem. Credit: Arris

(Image credit: Arris SURFboard SB6121 cable modem. Credit: Arris)

Several ISPs offer both DSL/cable and fiber options, so it can be challenging to determine which type of modem you need for your internet service even when you're looking at only one provider. If that's making your head spin, the good news is that your ISP will tell you which type of modem you need, and will even offer one for you to rent or, in some cases, buy.

A warning about renting your modem, though: It can cost you. While tacking on an extra $8 to $10 to your bill each month may not seem like much, those costs add up over time. A Comcast customer would pay $120 a year renting a cable modem from that ISP, for example; buy your own modem, and it's paid for itself after seven or eight months.

If you plan to keep the same internet service for more than a year, you're much better off buying your own modem, which will run you from $50 to $100 if you're looking for a cable modem. All you need to do is check with your ISP to make sure that the model you want to buy works with that provider's service. If you get cable internet, check out our recommendations for the best cable modems you can buy right now.

Routers: Taking the web wireless

Picking a modem is only half the battle, because they typically provide connections for just a single, wired device. If you want to go wireless, you're going to need a router, which is a networking device that lets you share your modem's internet connection with all your devices. Routers connect to your modem via an Ethernet cable and pass that internet connection on to other devices in your house either via an additional Ethernet cable or wirelessly over a Wi-Fi network.

D-Link AC5300 router. Credit: D-Link

(Image credit: D-Link AC5300 router. Credit: D-Link)

Routers come in two primary variants: standard single-unit routers (which can look a bit like spiders — looking at you, D-Link), and whole-home Wi-Fi routers that use multiple devices to create a mesh network that extends your Wi-Fi signal. For smaller homes, single-unit routers generally provide a good enough signal to provide a strong wireless connection to all corners of your home. (And if they don't, you can always pick up a Wi-Fi extender.)

MORE: How to Set Up Your Wi-Fi Extender for the Best Signal

For larger homes, whole-home Wi-Fi mesh networks are the better option. These mesh routers replace a single router with multiple Wi-Fi points (called nodes). Placed strategically throughout your home, they connect together seamlessly to blanket your home with wireless coverage, without any speed loss or coverage dead zones.

As with cable modems, we've looked at all types of routers and can recommend the best router for your home, with picks based on overall performance, range, price and how well the router handles online gaming.

Combination Modem-Routers: Not the best of both worlds

To complicate things, many ISPs and networking device makers offer combination devices that function as both modems and routers. It's a tempting proposition: You've only got to make room for one multitasker device instead of two pieces of gear performing different functions. But your network will be much better if you use a separate modem and router.

With the growing focus on wireless connections, advances in router technology occur much faster than in modem technology. One such advance is "multiuser multiple input, multiple output," or MU-MIMO, technology for Wi-Fi, a technology found in superfast (802.11ac) networks that can direct separate streams of bandwidth to as many as four different devices simultaneously, without losing bandwidth.

Credit: Shutterstock/JeDo_Foto

(Image credit: Shutterstock/JeDo_Foto)

Non-MU-MIMO devices share a single bandwidth pool, so checking social media on your phone while streaming a movie or TV show on your laptop, for example, makes both devices a little slower. MU-MIMO technology is just one example of a newer, advanced wireless technology that exists in several new routers, but in only a few combination devices.

Keeping your modem and router separate lets you update each device on an as-needed basis, upgrading whichever part of your home networking setup will give you the fastest network available. The annual CES trade show, which kicks off Jan. 9, will likely introduce several new routers that promise faster and more efficient speeds. If any of those new routers catch your eye, you'll be able to upgrade while keeping your old, reliable modem in place — at least assuming you're not using a hybrid modem-router.

Buying separate devices also makes it more convenient to troubleshoot when something goes wrong. If your router is fine and the modem is on the fritz (which is typically the case, in my experience), it's much easier to get a new modem. When replacing just the modem, you can simply plug it in and get back online.

If you are replacing a combination device, not only do you need to plug it in, but you also need to reconfigure your wireless network to get it back to the way you like it and get your devices reconnected.

  • JohnRS
    Perhaps you should have also mentioned that Routers with WiFi are actually two devices in one: A Router and a WAP (WiFi Application Point). I think that this is important for those who want a good router, which normally does not come with a WAP.