The big picture
A network is simply a group of devices that can talk to each other. Your office or home network connects laptops, phones, printers and other equipment, and links them to the wider internet through a service from an internet provider.
It helps to think of the network as a small town with a single road out. Devices inside the town can reach each other directly. To reach the outside world, everything goes through one gateway, and that gateway is your router.
The main pieces
Modem
The modem connects your building to your internet provider’s line, whether that is a cable, fiber or phone line. It translates between the provider’s signal and the type of connection your network uses. Many providers supply a single box that combines a modem and a router, which is why people often confuse the two.
Router
The router sits between your local network and the internet. Its jobs include:
- Directing traffic between your devices and the internet.
- Giving each device an address on your local network.
- Sharing the single internet connection among everything on the network.
- Usually acting as a basic firewall, blocking unsolicited connections from outside.
Switch
A switch adds extra wired connections. If your router has only four network sockets and you need more, a switch expands them. Many routers include a built-in switch.
Wireless access point
Wi-Fi is the part that lets devices connect without cables. Most home routers include a Wi-Fi access point. In larger offices or buildings with thick walls, extra access points connected by cable can provide better coverage than a single device in the corner.
How Wi-Fi works, in brief
Wi-Fi uses radio signals to carry network traffic between your device and the access point. A few practical points follow from this:
- Range and obstacles. Distance, walls, floors and metal objects weaken the signal. Placing the router in a central, open position generally helps.
- Bands. Most equipment offers more than one radio band. Lower-frequency bands usually reach farther through walls, while higher-frequency ones tend to be faster at short range. Devices often choose automatically.
- Shared airtime. Many devices on one access point share its capacity, and nearby networks can interfere. A busy office may need more than one access point.
- Network name and password. The network name (SSID) identifies the network. The password protects it. Modern security standards for Wi-Fi are named WPA2 and WPA3; choose the newest one your devices support, and avoid open networks or old WEP security for anything private.
For a business, it is a good habit to run a separate guest network for visitors and for smart or connected devices, so they cannot reach your business computers. The same idea applies to a connected home, and the basics of home Wi-Fi setup are covered in more detail elsewhere.
IP addresses
Every device on a network needs an address so data knows where to go. This is the IP address, a string of numbers (or numbers and letters) that identifies a device on a network.
There are two kinds worth knowing about.
Private (local) addresses are used inside your network. Your router hands them out so your laptop, phone and printer each have their own. These addresses only mean something inside your network, and many other networks use the same ranges. Common examples look like numbers beginning with 192.168 or 10.
Public addresses are the address the outside world sees. Your internet provider assigns one to your connection, and every device on your network typically appears to the internet as that one shared address. A function in the router called network address translation keeps track of which internal device asked for what.
Public addresses can be static (fixed) or dynamic (changing from time to time). Most small customers receive dynamic addresses unless they pay for a fixed one, which may be needed to host certain services.
Inside your network, addresses are usually assigned automatically by a service on the router called DHCP. This is why a new phone can join your Wi-Fi and work without anyone typing in numbers. If you have a printer or other device that others must always find at the same place, you can set a reservation on the router so it keeps the same address.
DNS: the phone book
People use names such as a website’s address; computers use numbers. DNS, the Domain Name System, translates one into the other. When you type a web address, your device asks a DNS server for the matching IP address, then connects to it. Your router usually passes these requests on to your internet provider’s DNS service, although you can choose another one. If DNS fails, websites may seem unreachable even though your connection is working.
Putting it together: what happens when you open a web page
- Your laptop connects to the Wi-Fi access point and receives a local IP address from the router.
- You type a web address. Your laptop asks DNS for the matching IP address.
- The request travels to the router, which sends it through the modem to your provider and onward across the internet.
- The website’s reply returns to your router, which passes it to the right device on your network.
All of this normally takes a fraction of a second.
Basic steps to keep a small network healthy and safer
- Change the router’s admin password. Default logins are widely known. Use a strong, unique password and store it in a password manager.
- Update the router’s firmware. Manufacturers release fixes for security flaws, much as with other software updates.
- Use strong Wi-Fi security (WPA2 or WPA3) and a long, unique Wi-Fi password. Change it when staff leave or if it has been widely shared.
- Turn off remote administration of the router unless you need it.
- Create a guest network for visitors and unmanaged devices.
- Know what is connected. Check the router’s device list from time to time. Unfamiliar devices deserve a question.
- Write down the essentials: the router’s location, login, provider’s contact details and account number. These are very useful when an outage hits.
Simple troubleshooting
When the internet seems down, a few questions narrow things down quickly:
- Is it one device or all of them? One device points to that device or its Wi-Fi connection.
- Does a wired connection work when Wi-Fi does not? That suggests a Wi-Fi problem.
- Are the lights on the modem and router normal? Your provider can explain what the lights mean.
- Does restarting the router and modem, waiting a couple of minutes between steps, help?
- Is your provider reporting a problem in your area?
If none of this resolves things, contact your provider or support person with what you have found. Having tried these steps and noted the results saves time.
Understanding these few parts will not make you a network engineer, but it makes it much easier to talk to support, spot something unusual and make sensible choices when you add equipment.