Hub, Switch and Router
What is inside the black box on the classroom wall?
- Distinguish hub, switch and router
- Explain what each device does with a packet
- Pick the right device for a job
Overview
Three devices sit at the heart of every LAN. They look similar but do very different things — and knowing the difference is what separates a helpful ICT student from a lucky one.
Hub
A hub repeats any signal it receives out of every other port — like shouting in a room. Simple and cheap, but wastes bandwidth and creates collisions. Effectively obsolete except in cheap toys.
Switch
A switch learns the MAC address behind each port and forwards frames only to the right port. This gives each device the full bandwidth of the link and eliminates collisions. Every classroom has one.
Router
A router moves packets between different networks, using IP addresses. Your home 'router' is really a switch + Wi-Fi access point + router in one box. Without it, your LAN would never reach the Internet.
Build a Mini LAN
- In groups, cable three PCs to a switch.
- Set IPs in the 192.168.1.x range and ping each other.
- Unplug one cable and observe: which PC loses connectivity, and does the rest of the network keep working?
- Which device uses MAC addresses to forward traffic?
Reveal answer
Switch.
- Which device connects two different networks?
Reveal answer
Router.
- Why is a hub considered obsolete?
Reveal answer
It floods every port, wasting bandwidth and creating collisions.
Look at the back of the school's main network box. Count the ports — is it a switch or a router?