Technology Explained

Modem vs. Router: The Differences and Why You Need Both

Simon Batt Updated 23-12-2019

Do you know the difference between a modem and a router? These two devices make up the backbone of our broadband experience, but not everyone understands how they fit together.

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Let’s break down the differences between the modem vs. the router and how each one plays its role.

What’s the Difference Between a Modem and a Router?

In short, a modem acts as a translator. It reads the data coming down the line from your ISP and converts it into a format that your computers and devices understand.

The router acts as a distributor by taking the data from the modem and sending it to your devices. It can also receive data from said devices and send it to the modem, back to the ISP.

The majority of households with an internet connection will use the two in tandem for the best experience. The modem handles the communication between your home and the ISP, and the router handles the communication between your home and the devices within it. There are exceptions to this, but for the most part, this is how people get online.

Now we know the basic difference between a modem and a router, let’s explore each one in-depth.

What Is a Modem?

The modem sits in-between the router and the line to your ISP. Its main job is to translate the messages coming from your ISP into something your computer can understand. Likewise, it can listen for your computers sending data and convert it into something you can send to your ISP.

Computers love digital signals. This is because digital speaks via ons and offs, which plays nicely with binary—the language of computers.

As such, if a signal that isn’t digital is sent to your PC, something has to translate it before it arrives. This is the modem’s main job—converting incoming signals into the computer-friendly digital format.

Typically, houses are connected to their ISP via copper cables or phone lines. These don’t use digital signals to send data; copper cables use electricity, and phone lines use analog signals. As such, the modem needs to convert these signals to digital, and vice versa.

The act of turning digital to analog and vice-versa is called “modulating” and “demodulating.” If you look at the start of these two words, you can see where the word “modem” comes from!

What Is a Router?

A router’s specialty is transferring data, so it’s equipped to handle data channels of all kinds (how does a router work? How Does a Router Work? A Simple Explanation Routers may seem complicated, but they're actually quite simple. Here's a quick guide to routers, what they do, and how they work. Read More ). You can plug an Ethernet cable into the back, or connect via 2.4 or 5Ghz Wi-Fi. The router also supplies Wi-Fi channels for your devices to use, and may also automatically select the best channel for your network.

Routers are more than just couriers, however. Some routers will have firewalls running on them to keep the connections secure. Some modern-day routers allow you to feed it some VPN details, and it’ll automatically route all the connections it receives toward that VPN’s server.

If you like the sound of encrypting all your outgoing data, be sure to read up on how to set up a VPN on your router How to Set Up a VPN on Your Router VPNs improve online privacy but running a VPN on every device is a pain. Here's how to install a VPN on your router and save time! Read More .

Modem vs. Router: Which Do You Need?

Most of the time, people will need both a modem and a router to get their homes online. However, there are some cases where you don’t need one or the other.

When You Don’t Need a Modem

Remember when we said that people are typically connected to their ISP via copper cables or phone lines? You may have raised an eyebrow at this claim, as there is the new kid on the block—fiber-optic.

If you look at how fiber-optic works, you’ll see that it sends data using light on/off pulses, much like a digital signal. So, why do you need a modem for this?

The reason why we didn’t mention fiber-optic above is that, typically, fiber-optic connections don’t go all the way into the home. They go the majority of the distance, then pass the baton to regular cables to cover the final stretch. These cables carry signals that need translating when they arrive.

If your fiber optic connection goes to a nearby utility box (Fiber-to-the-Curb, FTTC) or a neighborhood hub (Fiber-to-the-Node, FTTN), either copper or phone cables will cover the remaining distance to your home. As such, you need a modem to translate the data coming down the cable.

However, if you’re lucky enough to have a fiber-optic connection directly to your home (known as ‘Fiber-to-the-Home’, or FTTH), you should have a little box called an Optical Network Unit (ONU) somewhere. This would be installed in your home and decodes the light signals for you. As such, you don’t need a modem.

When You Don’t Need a Router

As we covered above, modems convert a signal into digital format, then pass it onto a router. But wait; what’s stopping you from directly attaching a computer to the modem? If it’s a digital signal, surely your computer can understand it without the need for a router?

In fact, there’s nothing stopping you from plugging your computer directly into the modem. You can take the modem’s Ethernet cable that usually goes to your router and plug it into a PC instead.

However, remember when we said that routers aren’t just couriers? They also play a role in keeping your computer safe from online dangers. Modems can’t do this; they just act as a translator.

As such, if you connect directly to your modem, you’re forsaking the security that a router can bring you. It’s not worth the trouble, so be sure to connect to a router instead!

But I Only Have One Device!

You may be confused, however, as to why you don’t have both a modem and a router. Instead, you have a single device that you plug directly into the line out, which also acts as a router for your Wi-Fi connections.

In this example, you’re the owner of a modem/router combo. These are becoming a popular choice, especially if you’re using a router your ISP gave you. Your one unit handles both the translation and distribution of data in one tidy package.

If you do decide to buy a router to replace it (and there are plenty of reasons to replace an ISP’s router 7 Reasons Why You Should Replace Your ISP’s Router Your ISP sent you a router when you signed up and it works fine. But is it giving you the best speeds possible? Read More ), take a look inside your modem/router’s settings. There’s a chance it supports “modem mode,” which disables the router functionality but keeps the modem portion. You can then plug a router into it and use it as a pure modem.

Demystifying Your Wi-Fi Network

All the parts that make up a Wi-Fi network can be confusing, but it’s quite simple in practice. A modem acts as a translator between you and your ISP, while your router handles all the devices that want internet.

If your head spins when thinking about Wi-Fi technology, why not read up on the most common Wi-Fi standards and types The Most Common Wi-Fi Standards and Types Explained Confused by the various Wi-Fi standards in use? Here's what you need to know about IEEE 802.11ac and older wireless standards. Read More ?

Explore more about: Buying Tips, Modem, Router.

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  1. Matthew
    September 13, 2017 at 4:40 am

    Is it possible to hook up the NETGEAR CM1000 using port aggregation to nighthawk 8? Only 1 Ethernet port on back of it but nighthawk 8 supports dual Ethernet aggregation and not sure if z switch could be used. I also have a NETGEAR 4G/LTE modem that has 2 (1) gigabit ports on it using an unlimited ATT card for connectivity. Can I hook both modems into the nighthawk router using ports 1 and 2 on the Nighthawk 8 to increase internet speed? Sry if this question is stupid, still learning the craft of setting up personal network
    Thanks in advance

  2. Victoria V Mason
    March 15, 2017 at 4:17 pm

    looking to hook it up to my playstation 4

  3. Victoria V Mason
    March 15, 2017 at 4:16 pm

    will it give me wifi without cable looking for wifi not any cable

  4. Linda mayer
    November 21, 2016 at 9:24 am

    I am impressed to see your great collection on some of effective laptops . Hopefully such helpful post will be continued .

  5. shaoul
    September 14, 2016 at 4:42 pm

    hi,
    there is a good amount of interresting informations provided, but i would like to add some:
    - 'if only 1 ethernet, it is a modem' most often true but not allways
    - '5 ethernet it is a router' yes for ethernet (wan) to ethernet (4*lan)
    but a modem-router would most often have only 4 ethernet and one specific port (cable or phone)
    - for x-dsl (adsl, vdsl, ...) you must choose a modem that is compatible (ask your isp)
    settings could be difficult if the isp does not give the correct info and the isp is not known by the modem
    - some isp provide voip services. then most often you must use the isp modem
    - you may also receive tv signal and there too a specific router/modem will be required

    this article speaks solely about the very low-cost end-user equipment (below 1K$) the professional equipments are way more expensive (REAL cisco, ...). even so the equipments presented here should be adequate even for sme's

    the provided info's seems very usa-centric. sorry, but 'US or ROW' (Rest Of the World) is so 'old time' now

    • Joel Lee
      September 20, 2016 at 12:50 am

      Hey Shaoul, thanks a lot for adding those details. You're right, especially the part about DSL connections requiring a different kind of modem than cable (because they use telephone lines, not coaxial cables). And yes, this was strictly with consumer equipment in mind, nothing about professional grade stuff.