A router joins networks and forwards data between them. When a device sends data to an address outside its own network, the router receives it, checks the destination address and sends it onwards towards the correct network.
This lesson sits in the networks and communication module and builds on the LAN and WAN ideas in choosing a network arrangement.
What does the router actually handle?
Data travels in packets: small pieces that each carry a destination address. A router reads that address, compares it with what it knows and passes the packet to the next link.
Home routers usually also act as a switch and a wireless access point. Those extras are common features, not the core job. The core job is forwarding packets between networks.
How is it different from a switch and a modem?
| Device | Main job |
|---|---|
| Switch | Connects devices inside one network and sends data to the intended device only |
| Router | Connects separate networks and forwards packets between them |
| Modem | Converts signals between the network and the line from the internet provider |
Local or outside? A step-by-step test
In this lesson the home network uses addresses beginning 192.168.1, so every address from 192.168.1.1 to 192.168.1.254 is on the local network.
- Read the destination address in the packet.
- Compare it with the local range. If it begins 192.168.1, it stays inside the network and the switch delivers it.
- If it does not, the device sends it to the router.
- The router forwards it to the internet provider, who passes it on towards the destination.
Worked example
A fictional laptop at 192.168.1.12 sends one packet to a printer at 192.168.1.40 and another to a web server at 203.0.113.45. The router’s address is 192.168.1.1.
Packet to the printer: the destination begins 192.168.1, so it is inside the local range. It stays on the local network and the router is not needed for delivery.
Packet to the web server: 203.0.113.45 does not begin 192.168.1, so it is outside. The laptop sends it to the router at 192.168.1.1. The router forwards it to the internet provider, and from there it travels across other routers until it reaches the server.
Reply: the web server sends its answer back to the router, which passes it to the laptop at 192.168.1.12.
The mistake to watch for
A common slip is to say the router “gives you internet” as if it produced it.
Mistaken answer: “The router is where the internet comes from.”
The internet is a worldwide set of networks. The router is one device that connects yours to it.
The correction is to describe the action: “The router receives packets, reads the destination address and forwards each one to the next network.” Another slip is to claim a router and a switch do the same job. A switch stays inside one network.
Check yourself
1. Is 192.168.1.200 local or outside, on a network using 192.168.1.1 to 192.168.1.254?
Show answer
Local. It begins 192.168.1 and falls inside the range, so the packet is delivered inside the network.
2. A packet is addressed to 192.168.2.5 from a device on that same network. Does it stay inside or go to the router?
Show answer
It begins 192.168.2, not 192.168.1, so it is outside the local range and goes to the router.
3. Give one job of a router and one job of a switch.
Show answer
Router: forwards packets between different networks, for example to the internet. Switch: connects devices within one network and sends data only to the intended device.
Where this leads next
Continue with comparing wired and wireless constraints to see how devices reach the router, and check your understanding in the practice set. Writing your own packet-journey notes is easier with the ICT practical task and evidence checker.
Seeing the journey of a message step by step is where students get stuck most. A teacher in online one-to-one ICT tuition can draw it with you and ask you to explain each hop.