Networking: Devices, Topologies & Protocols
🔒 Log in to trackNetwork devices
🔒 Log in to trackEach network device has one job. A hub broadcasts to all ports. A switch sends to the right port by MAC address. A router joins different networks by IP address. A modem converts digital and analog signals. Exams rarely name the device. They describe its job.
The device ladder
Learn each device with its layer and its one job.
| Device | Layer | What it does |
|---|---|---|
| Repeater | Physical (1) | regenerates a weak signal to extend range |
| Hub | Physical (1) | broadcasts every bit to every port; no intelligence |
| Bridge | Data Link (2) | joins two LAN segments and filters by MAC |
| Switch | Data Link (2) | learns MAC addresses and sends frames only to the right port |
| NIC | Data Link (2) | connects one machine to the network; carries its MAC |
| Access Point | Data Link (2) | puts Wi-Fi devices onto the wired LAN |
| Router | Network (3) | joins different networks and picks routes by IP |
| Gateway | up to Application (7) | converts between different protocol systems |
Tip: Hub is a dumb loudspeaker. Switch is a smart postman. Router is the link between cities.
Modem and firewall
A modem is a MOdulator-DEModulator. It turns the PC's digital data into analog signals for a phone or cable line. It turns analog back to digital.
A firewall is a rule filter in hardware or software. It allows or blocks traffic by rule. It can work at several layers.
The one-line differences
- Hub vs switch: a hub shouts to everyone. A switch sends only to the destination port. It is faster and safer.
- Switch vs router: a switch moves data inside one network by MAC. A router moves data between networks by IP.
- Repeater vs amplifier: a repeater regenerates a clean digital signal. An amplifier boosts the noise too.
- Gateway vs router: a router chooses routes. A gateway translates between protocol worlds.
Note: Your home router joins your LAN to the Internet.
MAC address, the burnt-in identity
Every NIC carries a 48-bit physical address, for example 1A:2B:3C:4D:5E:6F. The maker fixes it.
- MAC: physical and permanent. Switches read it.
- IP: logical and assigned. Routers read it.
A home network in four steps
Follow one message from a laptop to a website. This shows where each device sits.
- The laptop's NIC puts the data on the network. It carries the laptop's MAC address.
- An access point takes the Wi-Fi signal and passes it to the wired LAN.
- A switch sends the frames to the router's port only, using its MAC table.
- The router reads the IP address and forwards the packets to the Internet.
A modem sits between the router and the phone or cable line. It converts digital and analog signals.
Reading a device question
Find the verb first. Then name the device.
| Job in the question | Device |
|---|---|
| sends to all ports | hub |
| sends only to the destination port | switch |
| connects two different networks, chooses a path | router |
| regenerates a weak signal | repeater |
| converts protocols | gateway |
| digital to analog and back | modem |
Watch: When a layer is asked, use the ladder. No address is layer 1. MAC is layer 2. IP is layer 3.
Question types you will see
Each type: how to recognise it, the method step by step, and one question to try.
Hub vs switch vs router
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.
Sends to all ports: hub (layer 1).
Sends to the right port by MAC: switch (layer 2).
Joins different networks by IP: router (layer 3).
More intelligent than a hub: switch.
The job words point to exactly one device.
Which device forwards data only to the intended port instead of all ports?
Show solutionHide solution
Forwarding to one port needs a MAC table.
Hubs broadcast to every port.
A switch
Modem, repeater, bridge, gateway functions
A modem is used for, a device that regenerates a weak signal, or a device that converts between protocols. It is function-to-device matching.
Modem: digital signal to analog and back.
Repeater: regenerates weak signals.
Bridge: joins two LAN segments.
Gateway: translates between protocol systems.
Each device is named after its single job.
The device that regenerates and retransmits a weakening signal is a
Show solutionHide solution
Regenerating a signal is the repeater's job.
It restores the clean signal so the cable can run farther.
Repeater
Device-to-layer matching
A router works on which OSI layer, or a hub operates at layer what. It is a device and layer pair.
Hub and repeater: layer 1 (Physical).
Switch, bridge and NIC: layer 2 (Data Link).
Router: layer 3 (Network).
Gateway reaches up to the Application layer.
The address type a device reads fixes its layer.
A router operates on which layer of the OSI model?
Show solutionHide solution
A router uses IP addresses.
IP addresses belong to layer 3, the Network layer.
Layer 3 (Network)
NIC and MAC-address facts
A MAC address is how many bits, where it is stored, or how MAC differs from IP.
MAC is a 48-bit physical address.
The maker burns it into the NIC.
MAC is permanent. IP is assigned and changes.
Switches use MAC. Routers use IP.
MAC identifies the card. IP identifies the place in a network.
The physical address burnt into a network interface card is the
Show solutionHide solution
A burnt-in, factory-fixed address is physical.
The IP is only a logical label.
MAC address (48 bits)
Firewall and access point
A device that allows or blocks traffic by rules, or a device that lets Wi-Fi devices join a wired LAN.
Allows or blocks traffic by rules: firewall.
Joins wireless clients to a wired LAN: access point.
A firewall can be hardware or software.
An access point works at layer 2.
Both devices guard or open a door to the network.
Which device filters traffic by rules to allow or block it?
Show solutionHide solution
Rule-based allow or block is filtering.
That is a firewall.
Firewall
One-line device differences
Statements compare two devices: switch vs router, repeater vs amplifier, gateway vs router.
Switch: inside one network, by MAC. Router: between networks, by IP.
Repeater regenerates a clean signal. An amplifier also boosts noise.
Router selects routes. Gateway translates protocols.
Pick the option that matches the job.
Each pair differs in one key job.
Which device translates between different protocol systems?
Show solutionHide solution
A router only chooses routes.
Protocol translation is the gateway's job.
Gateway
Shortcuts that save time
Hub hears and shouts to all (layer 1). Switch is selective, by MAC (layer 2). Router routes between networks by IP (layer 3). 'Broadcasts to all' means hub. 'MAC address table' means switch. 'Connects two different networks' means router.
Which device forwards data only to the intended port using MAC addresses?
Show solutionHide solution
Selective forwarding is the switch's job.
The MAC table decides the port.
Switch
The full form is the answer. Digital data is modulated onto an analog carrier and demodulated back. 'Digital to analog conversion' in a question means modem.
Which device converts digital signals to analog and back?
Show solutionHide solution
Modulate means digital to analog.
Demodulate means analog to digital.
Modem
Mistakes to avoid
Where most students lose marks on this subtopic.
Saying a hub forwards data selectively.
That is the switch. A hub always broadcasts to every port.
Placing the router at the Data Link layer.
A router reads IP addresses, so it sits at the Network layer (3).
Confusing a gateway with a router.
A gateway converts protocols. A router selects routes.
Thinking the MAC address changes with the network.
MAC is permanent and physical. The IP is the one that is assigned.
Quick revision
Read this the night before the exam.
Hub broadcasts (layer 1). Switch learns MAC and sends to the right port (layer 2). Router routes between networks by IP (layer 3).
Repeater regenerates a signal (layer 1). Bridge joins two LANs (layer 2).
Gateway is a protocol converter.
Modem is a modulator plus a demodulator (digital to analog and back).
NIC carries the 48-bit MAC address.
MAC is permanent and physical. IP is logical and assigned.
Practice: 15 questions
Sets of 10, mixed across the question types above. Every answer has a step-by-step explanation.
Topic test · 10 questions
Suggested time 5 min · wrong answers go to your mistake notebook automatically.