Lesson
Switches
Learning objective
Explain how switches connect local devices and associate devices with ports at an introductory level.
What is a switch?
A switch connects devices in a local network. It is the modern, multi-port development of the bridge idea: instead of treating all connected devices as one shared signal space, it can be selective about which port carries local traffic.
Picture a switch as the central connection point for nearby hosts. A laptop, printer, and server can each use a separate cable while still belonging to the same local network.
The laptop sends to the printer. The switch uses Port 3; the other hosts receive no copy of this frame.
Highlighted cables show this frame's path; grey cables are still connected. This example assumes the switch already knows the destination port. Unknown destinations and broadcasts behave differently—you will explore them in the Data Link Layer module. On small screens, swipe across the diagram.
Switch ports
Each physical switch port is a labelled connection point for a host or another network device. If a printer cable is plugged into Port 3, Port 3 is the physical path between that printer and the switch.
At this stage, remember the simple relationship: one cable connects a device to one switch port. The detailed learning and forwarding process belongs in the Data Link Layer module.
More selective than a hub
A hub repeats an incoming signal to all other active ports. A switch can use the port that leads toward the relevant local device instead of treating every port the same. This makes switches a better fit for modern local networks.
For now, focus on the result: traffic for the printer can use the printer's path. Later, you will learn how a switch builds and uses its forwarding information.
Hub → bridge → switch: what changed?
- Hub: repeats the incoming signal to every other connected host.
- Bridge: separates shared segments and can keep known same-side traffic from crossing to the other segment.
- Switch: extends the bridge idea to many ports, so local devices can have separate connections and known-destination traffic can use the appropriate port.
These are three different arrangements—not devices that must all sit in one chain. A switch is not an Internet connection by itself, and it does not always send to only one port: unknown destinations and broadcasts are covered later.
Switches and routers
A switch primarily connects devices inside one local network. A router connects different IP networks and can provide a path beyond the local network. Home equipment may combine both functions in one box, but the two roles remain different.
Match hosts to ports
Follow the visible cables and choose which labelled switch port leads to the printer. Selecting a port sends the teaching frame through that path so you can check the decision.
Match a host to a switch port
Switch ports connect local devices. Follow the printer cable, then choose the port the switch should use.
Which labelled port leads to the printer?