They still forward packets, but today’s routers do so much more
By most definitions, the network router’s purpose is defined by its name—it routes packets from one location to another. But over the course of decades of internet networking, the value of the router has grown significantly, offering enterprises additional functions such as network security, content filtering, quality of service, and more.
At its most basic level, a router is a device that connects networks to each other, forwarding data packets from one location to another until they reaches their destination. Within a local area network (LAN), a router can also allow multiple devices to use the same Internet connection, such as how a home router allows users to connect their laptops, phones and tablets (among countless other devices) at the same time.
How does a router work?
Digital content, whether it’s an email being sent from an employee to a customer, or a real-time videoconferencing call, is delivered across the enterprise network and the global internet in the form of packets. These packets contain the destination address; for example, an IP address if the data is going across the internet.
The router determines the fastest path (or “route”) for the packet to deliver its payload. This is similar to how a GPS app on a smartphone might calculate the fastest route to a destination with all of the turns and which roads to take, but also factoring in real-time traffic conditions.
One key difference is that each individual router along the way does not determine the complete route, but rather just the next connection on the way to the final destination. The router does this by consulting an internal routing table – a list of paths to various network destinations.
The router reads the packet’s header to determine where it needs to go, then forwards the packet to the next network router in the most efficient path. Many routers also include the ability to both inform other packets about which routes to take, or forward packets to different routes for a given destination based on current conditions (such as heavier network traffic). This is commonly known as dynamic routing or adaptive routing, compared to static routing in which routes through a network are generally the same paths.
Within a home or small office network setup, the router is connected to a modem or gateway that connects an internet connection (typically broadband provided by an Internet Service Provider) to the home or business. Routers include ethernet ports to connect devices to the network, or they provide wireless functionality (via Wi-Fi) to connect devices such as laptops, smartphones or tablets.
A home or small office typically only needs one network router in order to provide LAN connectivity and internet connectivity. Midsize companies and enterprises typically utilize multiple routers to connect devices within a LAN, and then to an edge router in order to connect to the Internet (see below for different router types).
What is the difference between a router and a switch?
Routers are sometimes confused with switches, which also offer forwarding and routing of network traffic, but have different purposes. Routers operate at Layer 3 – the network layer – and are basically used to connect networks to other networks.
Switches, on the other hand, typically operate at Layer 2, connecting and sorting packets to distribute traffic to devices within the LAN. Some switches can operate on Layer 3, and some routers can perform switching tasks, but in general switches operate on the LAN, and routers typically connect LANs to the Internet and other routers on wide-area networks (WAN).
What is the difference between a router and a modem?
A modem (or gateway) is the device that connects the internet link provided by an ISP (typically a broadband connection, such as cable, fiber or DSL) to the home or business. The modem or gateway can then be connected to the router to provide either a direct wired connection to a single computer, or more typically to provide multiple connections to devices on the LAN – computers, phones, tablets, game consoles, TVs, refrigerators, etc.
What are the different types of routers?
Routers come in many different sizes, depending on the number of devices that need to be attached, or the functionality of the router. In general, a router falls into one of the following categories:
Core router: Typically used by large enterprises, ISPs and cloud service providers, these types of routers transmit high volumes of data packets within the network. Sometimes these core routers are part of the “Internet backbone”. They typically operate at the “core” of a network, hence their name.
Edge router: An edge router is basically the router that communicates with core routers and external networks, typically residing at the “edge” of a network. These networks utilize Border Gateway Protocol (BGP) to send and receive data from other LANs and WANs.
Wired router: These routers typically include ethernet ports that allow for LAN connections for devices that utilize ethernet for their main networking connection. Other networking devices in a data center, as well as older desktop computers that do not have wireless functionality, will connect to a wired router.
Wireless router: Similar to a wired router, these routers include a wireless radio that converts the digital signals into radio waves. A laptop or other mobile device will typically send data wirelessly to one of these routers. Within a large organization, wireless access points (not routers) help transmit data to a wired router before the data gets sent over the internet. However, some wide-area routers (such as a 4G or 5G wireless card that can be attached to a laptop) provide Internet connectivity, and include a wireless router inside them. For example, a smartphone that can share its 4G/5G connection with other users basically acts like a wireless router.
Virtual router: Software applications that perform the same functions as a hardware router – this is typically used in software-defined networking (SDN)
What are some other functions of routers?
Increasingly, routers are performing additional functions for a business, with features either placed onto a router itself, or the router connecting other hardware devices to perform those tasks. For example:
Firewall: Many routers include firewall functionality to prevent malicious traffic from entering the network, or they can attach a standalone firewall network device (in cases of larger businesses).
Quality of Service (QoS): For companies that need to prioritize specific types of traffic over others, such as videoconferencing over emails, QoS functionality can create those priorities (much like creating a high-occupancy vehicle lane on a highway that gives priority to carpools).
Multiple network setups: Routers can create guest networks that provide internet access only, restricting access to other devices on a LAN, or routers can work with network access features that limit which end users on a network can access specific servers or computers on the LAN (such as restricting most employees from human resources servers or files).