One box, several jobs
The device most people call a router is usually several devices in one casing. Depending on the model, it combines a router, a small network switch, a Wi-Fi access point and a basic firewall, and sometimes a modem as well. Knowing which job does what makes sense of the settings page and of what happens when something fails.
Job 1: Directing traffic between networks
The core job gives the device its name. A router sits between two networks: the one inside your home and the one belonging to your provider. When a device sends data to somewhere outside, the router forwards it toward the provider. When replies arrive, it decides which device in the house they belong to and passes them on.
This forwarding is based on addresses. Every packet of data carries a destination, and the router consults its tables to choose the next step. Providers’ routers do the same thing on a much bigger scale, passing data along from one network to the next until it reaches its destination.
Job 2: Sharing one connection
Your provider typically gives your home a single public address. Without a router, only one device could use it. The router solves this with a technique called network address translation, usually shortened to NAT. Inside the house, each device has its own private address, and the router keeps a record of which device made each request. When a reply comes back to the shared public address, the router uses that record to forward it to the right device.
A side effect is that the router blocks unsolicited connections from outside by default, because it has no record of any device having asked for them. This is a basic protection, though not a complete one.
Job 3: Handing out addresses
Most routers also run a service called DHCP. When a phone or laptop joins the network, it asks for an address, and the router assigns one from a pool, along with other settings the device needs, such as where to send its name lookups. This happens automatically, which is why you rarely need to configure anything when you join Wi-Fi.
Addresses are normally loaned for a set period and then renewed. If you want a particular device, such as a printer, to keep the same address, many routers let you reserve one for it in the settings.
Job 4: Connecting devices by cable
The numbered sockets on the back are usually a built-in switch. It lets wired devices talk to each other and to the router. If you run out of sockets, you can plug in an extra switch, which is a simple and inexpensive way to add more. A wired connection avoids sharing airtime with the Wi-Fi.
Job 5: Broadcasting Wi-Fi
The wireless part is technically an access point, which converts between radio signals and the wired network inside the box. It broadcasts your network name, checks the password and encrypts the traffic between the router and each device. Most modern models can use several frequency ranges at once and may offer a separate guest network.
The Wi-Fi radio is the component most affected by physical placement. A router tucked behind a TV or inside a cabinet usually provides weaker coverage than the same router on open shelf space in a central position.
Job 6: Basic security
Beyond NAT, routers often include a firewall that decides which connections are allowed in or out, and some offer extras such as parental controls, guest networks or the ability to run a virtual private network connection. These features vary a lot by model, and the defaults are usually reasonable for a home.
Because the router is the front door of the home network, keeping it secure matters more than most gadgets:
- Change the default administrator password. A password manager can store a long, unique one.
- Use a strong Wi-Fi password and modern encryption, which is typically labelled WPA2 or WPA3.
- Install software updates when they are available, or turn on automatic updates if your router offers them.
- Switch off remote administration unless you know you need it.
Router, modem and gateway
These words are often mixed up. A modem links to your provider’s line. A router manages the network inside your home. A gateway or combination unit supplied by a provider contains both. If you replace your own router, you might leave the provider’s box doing only the modem job, or put it into a bridge mode so that the two do not both try to run the network.
Using a guest network
A guest network is a separate Wi-Fi name with its own password, often isolated from your main devices. It is useful for visitors, and some people also use it for smart gadgets that don’t need access to their computers. It keeps the devices from the internet of things away from the laptops where you handle banking and email, which is a sensible precaution, though the results depend on how the router implements it. Using it when you share your connection is also much safer than relying on a public Wi-Fi hotspot elsewhere.
When to replace the box
An older router may lack support for newer Wi-Fi standards, no longer receive updates, or simply be too weak for the number of devices you have. Signs include frequent disconnections that a restart temporarily cures, an inability to get the speed your plan should give by cable, or a lack of security patches. If the box is supplied by your provider, ask what is allowed before swapping it. Replacing equipment will not help if the real problem is the line outside.