CAP7001 · Unit 2: Physical layer
Networking devices
10 practice questions · in the MTE and ETE syllabus
Key points
- Repeater and hub: physical layer
- Switch: data link, MAC-based forwarding
- Router: network layer, IP-based
- Switch splits collision domains; router splits broadcast domains
Networking devices are classified by the highest layer they work at.
| Device | Layer | Behaviour |
|---|---|---|
| Repeater | Physical | Regenerates a weak signal; no address knowledge |
| Hub | Physical | Multiport repeater; copies a signal to every other port |
| Switch (bridge) | Data link | Learns MAC addresses; forwards frames only where needed |
| Router | Network | Forwards packets between networks using IP addresses |
A switch builds an address table from the source MAC of arriving frames. If the destination is unknown it floods the frame out of every port except the arrival port; once learned, it forwards only to that port.
Worked example: a frame arriving on a 5-port hub leaves on 4 ports. Eight PCs on an 8-port switch form 8 collision domains, whereas on a hub they form 1.
Exam pitfall: a switch separates collision domains but not broadcast domains (without VLANs). Only a router separates broadcast domains. A hub does neither.
Try two questions
A repeater operates at which layer and what does it do?
- Network layer; routes packets
- Physical layer; regenerates the signal
- Transport layer; opens connections
- Data link layer; filters frames by MAC
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B. A repeater regenerates a weakened signal; it has no knowledge of addresses.
Which device filters traffic using MAC addresses and works at the data link layer?
- Modem
- Switch
- Repeater
- Hub
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B. A switch learns MAC addresses and forwards frames only to the destination port.