Networking: Devices, Topologies & Protocols
🔒 Log in to trackNetwork devices
🔒 Log in to track| Device | OSI layer | Job |
|---|---|---|
| NIC (Network Interface Card) | 2 | Connects a machine to the network; carries the burned-in 48-bit MAC address |
| Repeater | 1 | Regenerates a weakened signal to extend range |
| Hub | 1 | Multi-port repeater: broadcasts every bit to every port; no intelligence, half-duplex |
| Bridge | 2 | Joins two LAN segments, filtering by MAC |
| Switch | 2 | Learns a MAC-address table and forwards frames only to the destination port; full duplex |
| Router | 3 | Routes packets between different networks using IP addresses; the home gateway to the Internet |
| Gateway | up to 7 | Converts between different protocol architectures ('entrance/exit door' of a network) |
| Modem | - | MOdulator-DEModulator: converts digital <-> analog for phone/cable lines |
| Access Point | 2 | Bridges Wi-Fi clients onto the wired LAN |
| Firewall | - | Hardware/software rule-filter that allows or blocks traffic (can sit at several layers) |
Memory hooks: hub = dumb loudspeaker; switch = smart postman (MAC table); router = intercity network connector (IP).
Detailed notes
The device ladder — hub to gateway
| Device | Layer | What it does |
|---|---|---|
| Hub | Physical (1) | joins many machines; broadcasts every bit to every port — no intelligence |
| Switch | Data Link (2) | learns MAC addresses and sends frames only to the right port |
| Router | Network (3) | joins different networks and chooses routes using IP addresses |
| Repeater | Physical (1) | regenerates a weak signal to extend the cable's range |
| Bridge | Data Link (2) | joins two LAN segments, filtering local traffic |
| Gateway | up to Application | a protocol converter between different systems ("entry/exit door" of a network) |
| Modem | — | MOdulator-DEModulator: digital data of the PC to the analog phone line and back |
| NIC (Network Interface Card) | 2 | the card that connects one machine to the network; carries its MAC address |
| Access Point | 2 | lets wireless devices join a wired network (Wi-Fi) |
The one-line differences exams ask
- Hub vs Switch: hub shouts to everyone; a switch forwards only to the destination port — faster and safer.
- Switch vs Router: a switch moves traffic inside one network (by MAC); a router moves traffic between networks by IP and picks the best path — your home router joins your LAN to the Internet.
- Repeater vs Amplifier: a repeater regenerates the clean digital signal; an amplifier would boost the noise along with it.
- Gateway vs Router: a router selects routes; a gateway translates between different protocol worlds (e.g. a mail network to a phone network).
- Modem: the name is the definition — modulate (digital to analog) + demodulate (analog to digital).
MAC address — the burnt-in identity
Every NIC carries a 48-bit physical address (written like 1A:2B:3C:4D:5E:6F) fixed by the maker. The MAC is physical and permanent; the IP is logical and assigned. Switches read MACs; routers read IPs.
Reading a device question in the exam
Find the verb first: "sends to all ports" = hub; "sends only to the destination" = switch; "connects two different networks / chooses a path" = router; "regenerates a weak signal" = repeater; "converts protocols" = gateway; "digital to analog and back" = modem. Exams rarely name the device — they name its job. And when the layer is asked, remember the ladder: no brain (L1) < MAC reader (L2) < IP reader (L3).
Quick revision
- Hub = broadcast (L1); Switch = learns MAC, sends to the right port (L2); Router = routes between networks by IP (L3).
- Repeater regenerates signals (L1); Bridge joins two LANs (L2); Gateway = protocol converter.
- Modem = modulator + demodulator (digital to analog and back).
- NIC carries the 48-bit MAC address; MAC permanent, IP assigned.
Types of questions asked
Every way this subtopic shows up in exams — how to recognise it, the formula or logic to use, and a solved example.
Type 1: Hub vs switch vs routervery common4 practice Q
A behaviour is described (sends to all ports, forwards to the right port, connects two networks and picks a path) and the device is asked.
- Hub: broadcasts every bit to every port — no intelligence (Layer 1).
- Switch: learns MAC addresses, forwards frames to the correct port only (Layer 2).
- Router: connects DIFFERENT networks and routes packets by IP address (Layer 3).
- 'Which device is more intelligent than a hub?' = switch; 'which joins two networks?' = router.
Example: Which device forwards data only to the intended port instead of all ports?
A switch — it reads MAC addresses; a hub would broadcast to every port.
Type 2: Modem, repeater, bridge, gateway functionscommon4 practice Q
'A modem is used for', 'device that regenerates a weak signal', 'device that converts between protocols' — function-to-device matching.
- Modem = MOdulator-DEModulator: computer's digital signal to the analog line and back.
- Repeater: regenerates weak signals to extend range (Layer 1).
- Bridge: joins two LAN segments (Layer 2).
- Gateway: translates between different protocol systems — the entry/exit door.
Example: The device that regenerates and retransmits a weakening signal is a —
Repeater — it restores the clean digital signal so the cable can run farther.
Type 3: Device-to-layer matchingcommon3 practice Q
'A router works on which OSI layer?', 'a hub operates at layer ___' — device and OSI layer pairs.
- Hub, repeater = Layer 1 (Physical).
- Switch, bridge, NIC = Layer 2 (Data Link).
- Router = Layer 3 (Network) — it reads IP addresses.
- Gateway spans up to the Application layer.
Example: A router operates on which layer of the OSI model?
Layer 3 (Network) — routing decisions use IP addresses; switching by MAC happens on Layer 2.
Type 4: NIC and MAC-address factscommon2 practice Q
'A MAC address is ___ bits', 'where is the MAC address stored', 'MAC vs IP difference' questions.
- MAC = 48-bit physical address burnt into the NIC by the maker (like 1A:2B:3C:4D:5E:6F).
- MAC is permanent; IP is logical and changes with the network.
- Switches work on MAC (Layer 2); routers on IP (Layer 3).
Example: The physical address burnt into a network interface card is the —
MAC address — 48 bits, factory-fixed; the IP address is only a logical label assigned by software.
Shortcut tricks
⚡ Hub-Switch-Router ladder
Hub hears and shouts to all (layer 1); Switch = Selective, by MAC (layer 2, same network); Router = Routes between networks by IP (layer 3). Exam verbs: 'broadcasts to all' -> hub; 'MAC address table' -> switch; 'connects two different networks' -> router.
Example: Which device forwards data only to the intended port using MAC addresses?
Switch.
⚡ Modem = modulator + demodulator
The full form itself is the answer: digital computer data is modulated onto an analog carrier and demodulated back. 'Digital to analog conversion' in a question = modem.
Example: Device that converts digital signals to analog and back?
Modem.
Where students lose marks
Saying a hub forwards selectively - that is the switch; hubs always broadcast.
Placing the router at the Data Link layer - routers work on IP (Network layer, 3).
Confusing gateway (protocol converter) with router (route selector).
Practice sets — 15 questions
Sets of 10, mixed across the question types above. Each answer comes with a step-by-step explanation.
Topic test · 10 questions
Suggested time 5 min · wrong answers go to your mistake notebook automatically.