Network Devices: Modem, Repeater, Hub, Switch, Router and Gateway (Class 12 Computer Science)
Updated 17 October 2026 · Fact-checked
Network devices are the hardware that connects computers into a network. A modem converts between digital and analogue signals, an Ethernet card connects a computer to a wired LAN, a repeater regenerates a weak signal, a hub broadcasts to all ports, a switch forwards data only to the intended port, a router connects different networks, and a gateway links networks that use different protocols.
Notice that the hub copies data out to every port, but the switch reads the address and sends it only to the intended computer.
Illustration drawn for QuestionBuddy.
Understand Network Devices: Modem, Hub, Switch, Router, Gateway
A network is a set of computers and other devices joined so that they can share data and resources. The devices below are the ones the CBSE syllabus names; each is asked for by job.
Modem. Short for modulator-demodulator. It converts the digital signals of a computer into analogue signals for a telephone-type line (modulation) and converts incoming analogue signals back into digital form (demodulation).
Ethernet card (network interface card, NIC). A card or chip inside a computer that connects it to a wired LAN. Every card carries a unique hardware (MAC) address, which identifies the computer on the local network.
RJ45. The eight-pin plug at the ends of an Ethernet twisted-pair cable. It fits the Ethernet card and switch ports.
Repeater. A signal weakens with distance in a cable. A repeater receives the weak signal, regenerates it and sends it on, so the network can span a longer distance.
Hub. A simple device with several ports. Whatever arrives on one port is broadcast to all other ports, so every connected computer receives it, and only the addressed one keeps it. All computers share the same capacity, which slows a busy network.
Switch. Looks like a hub but reads the destination address of the data and sends it only to the port of the intended computer. Fewer collisions and better use of the cable, so switches have largely replaced hubs.
Router. Connects two or more different networks (for example a LAN and the Internet), and chooses the path for each packet using the destination IP address. A home Wi-Fi box is usually a modem and router together.
Gateway. Connects networks that use different protocols or architectures and translates between them. It is the entry and exit point of a network.
Wi-Fi card. The wireless counterpart of the Ethernet card, which lets a laptop or phone connect through radio waves to a wireless access point or router.
Hub versus switch versus router. A hub is unintelligent and broadcasts; a switch is intelligent inside one network and sends to one port; a router works between networks and decides routes.
Network Devices: Modem, Hub, Switch, Router, Gateway: key facts
- Device and job
Modem digital to analogue and back Ethernet card connects a computer to a wired LAN RJ45 connector of twisted-pair cable Wi-Fi card wireless network connection - Learn each as a one-line job.
- Signal and traffic
Repeater regenerates a weak signal Hub broadcasts to all ports Switch sends only to the destination port - Switch is better than hub for a busy LAN.
- Between networks
- Router: connects different networks and chooses paths | Gateway: connects networks with different protocols
- Router uses IP addresses to forward packets.
- Hub switch router
Hub no intelligence, shared bandwidth Switch reads address, one port, one LAN Router links networks, picks routes - The usual three-point comparison.
How to answer Network Devices: Modem, Hub, Switch, Router, Gateway questions
For a device question, decide whether it asks for the name from a job or the job from a name, and answer in one line.
- 1Read the job in the question: weak signal, broadcast, selective forwarding, joining networks, translating protocols.
- 2Match to the device: repeater, hub, switch, router or gateway respectively.
- 3For a comparison, choose three fixed points: what it connects, how it sends data, and the kind of network it serves.
- 4For a case study, assign devices to places: a switch inside each building, a router at the Internet entry, a repeater only where the stated distance limit is crossed.
- 5Write the full form where one exists: NIC, RJ45 (do not guess an expansion), Wi-Fi card.
Network Devices: Modem, Hub, Switch, Router, Gateway in real life
The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.
Choosing a switch for the lab
Suppose a school lab with 20 computers shares printouts and files, and the teacher complains that the network slows down when many students copy data together.
Would replacing the hub by a switch help? Why?
Try it first, then show the solutionSolution
- A hub sends every frame to all 20 computers, so all of them share the same capacity.
- A switch sends each frame only to the port of the destination computer, so several pairs can talk at once.
Answer: Yes: a switch forwards only to the intended port, so traffic is less crowded.
Memory hook: A hub shouts in a room; a switch whispers to one person.
Weak signal on a long cable
Suppose two buildings of a campus are joined by a long cable and the connection works only intermittently.
Which device can be placed in the middle, and what does it do?
Try it first, then show the solutionSolution
- A weakening signal is the cause.
- A repeater regenerates the signal and passes it on.
Answer: A repeater, which regenerates the signal.
Memory hook: Like a relay runner who takes the baton fresh and runs again.
Tricks to remember Network Devices: Modem, Hub, Switch, Router, Gateway
Short memory aids. Say each one aloud once, then use it on a question the same day.
M-R-H-S-R-G
Modem, Repeater, Hub, Switch, Router, Gateway: the order from signal to between-network devices.
Use it when: Recalling all devices.
Hub = broadcast, Switch = selective
Hub shouts to everybody; switch addresses one port.
Use it when: Hub versus switch.
Router routes, gateway translates
Router chooses the path; gateway translates between different protocols.
Use it when: Router versus gateway.
Repeater repeats
It repeats (regenerates) the weakened signal.
Use it when: Long-distance cable questions.
Network Devices: Modem, Hub, Switch, Router, Gateway: solved examples
Ordered from board level to HOTS. Try each one before you open the solution.
Example 1: Modem · 1 mark · MCQBoard level
The device that converts digital signals into analogue signals and the reverse is called a:
(a) router (b) modem (c) switch (d) gateway
Try it first, then show the solutionSolution
- Modulation changes digital to analogue; demodulation changes it back.
- The device doing both is a modem.
Answer: (b) modem
Example 2: Hub or switch · 2 marks · Short answerBoard level
Differentiate between a hub and a switch.
Try it first, then show the solutionSolution
- A hub broadcasts the incoming data to all its ports, so every computer receives it. (1 mark)
- A switch reads the destination address and sends the data only to the port of the intended computer, so it is faster and more efficient. (1 mark)
Answer: Hub broadcasts to all ports; a switch forwards only to the destination port.
Example 3: Identify the device · 2 marks · Short answerHarder board level
Name the device in each case: (i) regenerates a weak signal in a long cable; (ii) joins a LAN to the Internet and chooses the path of data packets; (iii) joins two networks that use different protocols; (iv) fitted in a computer to connect it to a wired LAN.
Try it first, then show the solutionSolution
- (i) Repeater. (ii) Router. (iii) Gateway. (iv) Ethernet card (NIC).
- Each correct pair earns half a mark.
Answer: (i) Repeater (ii) Router (iii) Gateway (iv) Ethernet card (NIC)
Example 4: Three-point comparison · 3 marks · Short answerHarder board level
Compare a hub, a switch and a router on: (a) what it connects, (b) how it sends data.
Try it first, then show the solutionSolution
- Hub: connects computers within one LAN; it broadcasts the data to every port. (1 mark)
- Switch: connects computers within one LAN; it sends data only to the destination port. (1 mark)
- Router: connects different networks (for example LAN to Internet); it chooses the path for packets using IP addresses. (1 mark)
Answer: Hub: one LAN, broadcast. Switch: one LAN, one port. Router: between networks, chooses a path.
Example 5: Case: choosing devices · 4 marks · Case-basedHOTS / competency
Suppose a school wants to set up a lab network.
(i) Which device connects the 15 lab computers to each other so that data goes only to the receiving computer? (1 mark)
(ii) The lab must share an Internet connection from the service provider. Which device joins the lab LAN to the Internet and decides the path of data? (1 mark)
(iii) The distance between the lab switch and the principal's office is longer than the cable limit. Which device should be placed on the way? (1 mark)
(iv) A teacher's laptop with no network socket must join wirelessly. What does it need? (1 mark)
Try it first, then show the solutionSolution
- (i) A switch, which sends data only to the destination port.
- (ii) A router (the modem supplies the line signal).
- (iii) A repeater, which regenerates the weakened signal.
- (iv) A Wi-Fi card (an internal or USB wireless adapter).
Answer: (i) Switch (ii) Router (iii) Repeater (iv) Wi-Fi card
Where students lose marks in Network Devices: Modem, Hub, Switch, Router, Gateway
The slips examiners see most often, and what to write instead.
Mistake: Calling a switch a hub
A hub broadcasts; a switch sends only to the intended port.
Wrong working
A hub sends data only to the receiver.
Right working
A hub sends data to all ports; a switch sends to one port.
Do this: State "broadcast" for hub and "destination port" for switch.
Usually costs: 1 mark
Mistake: Saying a repeater amplifies noise
The idea is to regenerate the signal, restoring its shape, not merely boost it.
Wrong working
A repeater increases voltage.
Right working
A repeater regenerates the weakened signal.
Do this: Use the word regenerate.
Usually costs: 0.5 mark
Mistake: Mixing router and gateway
A router joins networks of the same protocol family and chooses paths; a gateway translates different protocols.
Wrong working
A gateway selects the shortest path.
Right working
A router selects the path; a gateway translates between different protocols.
Do this: Attach path to router and translation to gateway.
Usually costs: 1 mark
Exam tips
- Learn a one-line job for each device; most 1 and 2 mark questions are only that.
- In case studies use a switch inside each building, a router for the Internet, and a repeater only for the stated long distance.
- For hub versus switch, the word broadcast is the mark-carrying word.
- Do not add devices the question does not need.
- The Wi-Fi card is the wireless counterpart of the Ethernet card.
Practice questions on Network Devices: Modem, Hub, Switch, Router, Gateway
Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.
Q1 · 1 mark · MCQBoard level
The connector fitted at the ends of an Ethernet twisted-pair cable is:
(a) RJ11 (b) RJ45 (c) USB (d) HDMIHint
Eight-pin plug.
Answer
(b) RJ45
Q2 · 1 mark · Very short answerBoard level
What is the function of a repeater?
Hint
Think signal strength.
Answer
It receives a weakened signal, regenerates it and retransmits it, extending the distance of a network.
Q3 · 1 mark · Assertion-reasonHarder board level
Assertion (A): A switch gives better performance than a hub in a busy LAN.
Reason (R): A switch forwards data only to the port of the intended receiver.
(a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is not the correct explanation of A. (c) A is true but R is false. (d) A is false but R is true.Hint
Which device broadcasts?
Answer
(a) Both are true and R explains A: because data goes to one port, other computers are not disturbed.
Q4 · 2 marks · Short answerHarder board level
Explain the difference between a router and a gateway with one use of each.
Hint
One chooses a path, the other translates.
Answer
A router connects different networks and forwards packets along the best path using IP addresses (use: connecting a LAN to the Internet). A gateway connects networks that use different protocols and translates between them (use: joining a LAN to a network with a different architecture).
Q5 · 3 marks · Short answerHOTS / competency
Suppose a company has a LAN in its office and wants the LAN to reach the Internet, and one department uses a legacy system with a different protocol. Name the devices required and the job of each.
Hint
Two networks plus one protocol difference.
Answer
A router connects the office LAN to the Internet and forwards packets. A gateway translates between the legacy department network and the rest of the network. A modem is also needed if the line from the provider carries analogue signals.
Test your recall
Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.
1.What does a modem do?Show answer
Converts digital signals to analogue and back.
2.What does a repeater do?Show answer
Regenerates a weak signal.
3.Which device broadcasts data to all ports?Show answer
Hub.
4.Which device forwards data to only the destination port?Show answer
Switch.
5.Which device connects different networks and chooses the path?Show answer
Router.
6.A device translates between two networks built on unlike protocols. Name it.Show answer
Gateway.
Network Devices: Modem, Hub, Switch, Router, Gateway: frequently asked questions
What is the difference between a hub and a switch?
A hub broadcasts every incoming signal to all its ports. A switch reads the destination address and sends the data only to the port where the intended computer is connected.
Is a router the same as a modem?
No. A modem converts signals between the line and the computer. A router connects networks and chooses the path of packets. Home boxes often combine both.
What is an Ethernet card?
It is a card or chip in a computer, also called a network interface card (NIC), that connects the computer to a wired LAN and carries a unique hardware address.
Do I need to learn the full form of RJ45?
No. RJ45 is learnt as the standard connector of Ethernet twisted-pair cable; the syllabus asks for its role, not an expansion.