What Is a Router? Here’s Why You Need It for Internet
Find out how a router brings all your devices together in your home or office.
A router is a computing device that sits between your modem and your connected devices and relays internet and local data between them. It can be a standalone unit that connects to your modem using a single Ethernet cable or part of a single modem/router hybrid device. It’s also used for network management and hiding your local devices from the internet.
What is a router?
A router serves as a hub and firewall for local wired devices. It provides multiple ports for computers, game consoles, media streamers, and so on along with a port dedicated to communicating with the modem.
A Wi-Fi router (or wireless router) adds wireless devices to your local network in addition to supporting wired connections. A wireless router may have up to eight external antennas, while other models pack the antennas inside the chassis and are not visible.
A wireless gateway is a single unit that functions as the modem and the router. It typically includes several ports on the back for wired connections. The Wi-Fi antennas are internal or external, depending on the model.
Think of a router as a small computer dedicated to relaying only network traffic. It has a processor, system memory to temporarily manage data, two storage devices with the startup configuration and the diagnostic software, and flash-based storage for the operating system (firmware). On the back are several ports for wired Ethernet connections and one or two USB ports for network-shared storage.
External antennas on a wireless router generally provide better range and throughput. You can also maneuver these antennas so they can better broadcast signals into a specific location. Internal antennas, meanwhile, cannot be manipulated, so they broadcast in a set sphere.
In short, a router manages local network traffic and serves as the network’s public-facing address, hiding your devices from the internet.
From here on, we will refer to wireless routers since they’re the more common model used in households.
Why do we need a router?
You need a router because your internet connection starts at the modem, which typically has just one Ethernet port. A router adds additional Ethernet ports for wired devices and enables wireless connections to create a Wi-Fi network. A router is also required to manage all devices on your network from one central point.
Does a router require a modem for internet?
Yes, a router requires a modem for internet because the modem translates your provider’s internet signal into data your router and connected devices can understand.
Most land-based internet connections piggyback one of two types of cable already installed in your home or office: telephone and cable TV. These connections rely on electrical signals that move along copper wires. The only exception is fiber internet, which uses light pushed through thin optic fibers.
In all three cases, a router can’t natively read these signals, so the modem must revert (demodulate) these signals back into data that can be delivered through an Ethernet connection for local network use. After that, the router takes over and delivers data through an Ethernet or Wi-Fi connection.
Digital subscriber line (DSL) uses telephone lines and contains two electrical signals: analog (telephone) and digital (internet). A DSL modem separates and reverts the digital signal back into data that can be transferred through an Ethernet connection. The router receives this data through its Ethernet connection to the modem and delivers the data to a wired or wireless device.
Cable internet utilizes an unused 6 MHz television channel sent across thicker cable TV lines. It requires a different modem that separates this digital signal from the other TV signals and reverts it back into data that can be transferred through an Ethernet connection. The router receives this data through its Ethernet connection to the modem and sends the data to a wired or wireless device.
Fiber internet relies on two types of modems. If your ISP’s fiber network stops at the street, then your connection likely uses a cable modem. If your ISP provides fiber-to-the-premises, then your connection likely has a fiber modem.
Unlike DSL and cable modems, a fiber modem receives laser or LED pulses and reverts them back into data that can be transferred through an Ethernet connection. The router receives this data through its Ethernet connection to the modem and sends the data to a wired or wireless device.
If you’re interested in fiber internet, we provide a guide that shows you what you need to install fiber-optic internet.
How does a router work?
The router creates a directory (routing table) listing all your Wi-Fi and wired devices in order to receive and send their data to the internet. Since these devices have at least one physical address, the router automatically assigns a private IP address to these physical addresses using the Dynamic Host Configuration Protocol (DHCP).
Every connected device automatically receives an assigned private IP address, whether it’s a friend’s smartphone or a new laptop. There’s no manual configuration on your part.
For example, imagine that your router is a local postmaster that automatically assigns a private post office box (PO Box) to each device (or customer). No one can see the PO Box address except for you and the postmaster.
When your device sends a data packet, the postmaster replaces your return PO Box address with its own and makes a note in its ledger—including the destination address (website, game server, streaming service, etc.). The modem converts the packet and sends it on its way without looking twice.
When the router finally receives a response, it looks up the original destination address in the ledger and delivers the response to the appropriate PO Box. It then deletes that entry in its ledger, marking the exchange between the PO Box—your device—and the website as complete.
How does a router handle Wi-Fi?
When you access the internet using Wi-Fi, a wireless device must convert data into radio waves and use its internal antennas to transmit those radio waves to the router. The router receives those radio waves, converts the data for Ethernet, and delivers it to the modem.
When the router receives the response data from the modem, it retrieves the website’s address from the data and pairs it against the record in its table. It then converts the data into radio signals, transmits the dedicated signals through its antennas to the destination, and then deletes the record, closing the transaction.
While wireless connections are convenient, the conversion from radio waves to electrical waves adds latency to your connections. This conversion is why we will always prefer wired Ethernet connections versus Wi-Fi for gaming and media centers. Even with fiber internet, the conversion will always slow things down in addition to all the pitfalls associated with Wi-Fi (range, obstacles, interference, etc.).
How does a router handle Ethernet?
Unlike with Wi-Fi, there’s no need to convert data transmitted between the router and wired devices with Ethernet. When the router receives data from a wired device, it changes the source private IP address in the data, records the change, and then forwards it to the modem.
When the router receives the response data from the modem, it retrieves the website’s address from the data and pairs it against the record in its table. It then forwards the data through the associated LAN port to the target wired device and deletes the record, closing the transaction.
What else does a router do?
You might’ve read that you should never connect a computer directly to a modem, but that’s not true. As long as your computer has its firewall and antivirus switched on, there’s no reason why you can’t plug directly into a modem if you have no plans to use other devices—you do it to test your internet speed, after all. Plugging your computer in directly is no different than the dial-up days, although the internet is bigger, darker, and more populated.
But there’s a huge benefit to using a router—network management. For example, you can do the following with a router:
- Block specific wired and wireless devices
- Block or allow access to specific websites
- Prioritize data, like gaming or a favorite streaming service
- Create a guest connection, so you’re not sharing your primary password
- Limit the hours of use
- Create direct connections to specific devices
- Share files from a central location, like a USB
Routers ship with firewalls, providing an extra layer of security between your devices and the internet. The firewall inspects each incoming data packet to determine its validity. If the packet doesn’t pass inspection, then it is not forwarded to the appropriate destination. Here are two common firewalls provided in routers:
- Stateful Packet Inspection (SPI)—This firewall is quicker because it examines the nature of packets—where they are from, where they are going—and records this information.
- Deep Packet Inspection (DPI) — This firewall is slower because it examines each packet for malware and proper formation.
Router terminology to know
Demilitarized Zone (DMZ)
A DMZ serves as a buffer between your local network and the internet. It allows a single local device to appear “exposed” to the internet to host files, a game server, a Zoom conference, and so on. The user supplies the device’s MAC address or IP address (preferably static) as the destination and the IP address or IP address range as the source (public audience).
The problem with this feature is that the “host” device can still communicate with all other local devices. If you set up a public FTP and the device is compromised, the hacker can infiltrate your home network. Using DMZ for hosting online games is the next step if port forwarding doesn’t perform adequately.
Dynamic Host Configuration Protocol (DHCP)
This network management protocol automatically assigns IP addresses to devices accessing the local network. These addresses change if the network restarts or if the lease time ends. Assigned addresses typically last only 24 hours (1,440 minutes) unless you change this setting in the router’s interface.
Internet Protocol (IP) address
Everything connected to the internet needs an address, just like every house and building. Your internet connection (modem) has an IP address assigned by your ISP. Your network connection has a separate IP address seen only by local devices, not the internet.
Internet Protocol v4, the current standard, uses a 32-bit number divided into four 8-bit dotted-decimal numbers ranging from 0 to 255 each. Addresses reserved for private networks start with 10, 172, and 192.
The newer Internet Protocol v6 uses a 128-bit number divided into eight groups of four hexadecimal digits. IPv6 can support around 340 undecillion devices (2 to the 128th power) compared to 4.3 billion supported by IPv4 (2 to the 32nd power).
Local area network (LAN)
This is the wired and wireless network in your home or office. The term is typically associated with wired Ethernet connections to the router, but wireless devices are also part of the LAN.
Media access control (MAC) address
A MAC address is an identifier assigned to the NIC and/or WNIC of a device by the manufacturer. This address consists of six groups of two hexadecimal digits and cannot be changed. Modems and routers use this number to assign an IP address to the parent device.
Network Address Translation (NAT)
NAT translates private IP addresses to public ones. In this case, the router serves as the public-facing address and represents all devices connected to the local network. When you send data to the internet, NAT modifies each packet header so the source private address reads as the router’s public IP address, masking your device’s connection. The router then makes a record and delivers the data packet to the modem. When the destination sends a response, the router refers to the record and forwards the data to your device.
If you disable NAT, all data sent from connected devices will have their private IP address listed as the source rather than the router’s public IP address. The ISP may or may not reject this data. Moreover, ISPs cannot send response data to private IP addresses.
Disabling NAT also disables DHCP.
Network Interface Controller (NIC)
A NIC can be a physical card plugged into the motherboard inside older computers. Newer computers have an integrated NIC on the motherboard. Both versions include an RJ45 port for Ethernet connections—maybe even two.
Wireless devices use a wireless network interface controller (WNIC) that handles Wi-Fi and Bluetooth connections. Ethernet connections are possible using a USB adapter.
All data sent across a network is broken down into units called packets. Each packet consists of a header and a payload. The header contains the destination IP address, the source IP address, and information about the payload—this is what the router reads and modifies. The payload is your actual data.
For example, an email breaks down into packets that are delivered to the email server and compiled back into your message. A router typically alters the source IP address with its own public address to mask your device. It then records the transaction in the NAT table.
Think of your connection as a collection of docks, each assigned to a specific ship. One port handles only email sent through the Post Office Protocol (POP3), while another focuses only on email sent using the Simple Mail Transfer Protocol (SMTP).
When your client device connects to a website, the router replaces the device’s private IP address and associated port with its own public address. It then records the information about that specific connection in the NAT table.
Once the destination sends a response, the router forwards the data to the client device and deletes the NAT table entry.
With port forwarding, you keep one or more ports associated with a specific address open for business. For instance, if you have an Xbox Series X console, the ideal scenario would be to load the router’s interface and create a “static” IP address for the console’s connection—meaning if the network resets, the console keeps the private IP address.
After that, you would add a new Single Port Forwarding or Port Range Forwarding rule that would tell the router to send all Xbox Live traffic to a specific port associated with the console’s new IP address. Microsoft Xbox Live network requires you to route seven different ports for the best connection.
Quality of Service (QoS)
Also known as media prioritization, QoS allows you to allocate more bandwidth to specific devices and services. For instance, you can secretly set aside more bandwidth for Fortnite running on a Windows PC and less bandwidth for the tablet owner binge-watching Dr. Pimple Popper in bed.
The idea is for “critical” traffic to pass through the router first to improve performance for those applications. You can allow the router to prioritize traffic automatically or manually set the limits.
Universal Plug and Play (UPnP)
UPnP allows all networked devices and apps to discover each other. For example, this protocol will enable you to connect a discoverable printer that is accessible by other devices on the local network—no manual configuration needed. These devices can communicate through Ethernet, Wi-Fi, Radio Frequency Identification (RFID), and Bluetooth.
This feature is typically enabled by default, but you can toggle it off through the router’s interface.
Wide area network (WAN)
This is a network that spans a large geographical area—the internet, in this case. The term is typically associated with the wired Ethernet connection between your modem and your router.
Author - Kevin Parrish
Kevin Parrish has more than a decade of experience working as a writer, editor, and product tester. He began writing about computer hardware and soon branched out to other devices and services such as networking equipment, phones and tablets, game consoles, and other internet-connected devices. His work has appeared in Tom’s Hardware, Tom's Guide, Maximum PC, Digital Trends, Android Authority, How-To Geek, Lifewire, and others. At HighSpeedInternet.com, he focuses on internet security.
Editor - Cara Haynes
Cara Haynes has been editing and writing in the digital space for seven years, and she's edited all things internet for HighSpeedInternet.com for five years. She graduated with a BA in English and a minor in editing from Brigham Young University. When she's not editing, she makes tech accessible through her freelance writing for brands like Pluralsight. She believes no one should feel lost in internet land and that a good internet connection significantly extends your life span.