Computer ScienceCBSE Class 12 · Computer Networks

Types of Networks and Topologies: PAN, LAN, MAN, WAN, Bus, Star and Tree (Class 12 Computer Science)

Updated 17 October 2026 · Fact-checked

Networks are classified by area as PAN (around one person), LAN (a building or campus), MAN (a city) and WAN (countries or the world). A topology is the layout of the nodes: bus uses a single backbone cable, star connects every node to a central switch or hub, and tree joins star groups through a backbone.

Understand Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree

Types of network by area.

PAN (Personal Area Network): devices around one person, a few metres, for example a phone linked to wireless earphones by Bluetooth.
LAN (Local Area Network): a room, a building or a campus. High speed, owned by one organisation. A school lab is a LAN.
MAN (Metropolitan Area Network): a city or large town, joining several LANs. A cable TV network of a city is an example.
WAN (Wide Area Network): large regions, countries or the world, using public or leased links. The Internet is the largest WAN.

Topology is the way nodes and cables are arranged. The syllabus asks for bus, star and tree.

Bus. All nodes attach to one common cable, the backbone, with terminators at both ends.

Advantages: very little cable, cheap, easy to extend.
Disadvantages: a break in the backbone stops the whole network; slower when many nodes send; hard to find a fault.

Star. Every node has its own cable to a central device (a switch or hub).

Advantages: a failure of one node or cable does not stop the others; easy to add or find a faulty node.
Disadvantages: if the central device fails the whole network fails; more cable is used.

Tree. A hierarchy: several star networks (each with its own switch) are joined to a backbone.

Advantages: easy to extend, each group is managed separately, and a fault in one group does not stop another.
Disadvantages: the backbone and the top-level devices are critical points; more cable and devices; complex to manage.

Network design case (5 marks). The board paper gives buildings, distances and numbers of computers. The usual parts: place the server in the building with the most computers; draw a cable layout that avoids long links; state where a repeater is needed (the question gives the distance limit); suggest a switch/hub in every building; name the best topology (star for a building, tree for a campus); and a device or service for the Internet.

Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree: key facts

Types by area: PAN around one person, a few metres
LAN room, building or campus
MAN city
WAN country or world, the Internet is the largest; Larger area, usually slower and costlier.
Bus topology: Single common backbone
Terminators at both ends
Advantage: cheap, little cable
Disadvantage: backbone break stops all; Fault finding is hard.
Star topology: Each node cabled to a central switch or hub
Advantage: one node fault does not affect others
Disadvantage: central device failure stops all; Needs more cable than bus.
Tree topology: Star groups joined by a backbone
Advantage: easy expansion, group-wise management
Disadvantage: backbone and top device are critical; Combination of star and bus.

PAN	around one person, a few metres
LAN	room, building or campus
MAN	city
WAN	country or world, the Internet is the largest

How to answer Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree questions

For the 5-mark network-design case, answer each part in one or two lines using the data in the table.

1Server: choose the building with the highest number of computers.
2Cable layout: connect buildings by the shortest links and avoid any link longer than the distance limit given.
3Repeater: name the pair of buildings (or the cable) where the distance is more than the limit stated in the question.
4Topology: a star inside each building, and a tree or star between buildings; give a reason.
5Devices: a switch in every building, a router (or modem) for the Internet; name the best wired medium if asked (optical fibre for long and fast links).
6If a calculation is needed (total cable, number of computers), show it in one line.

Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree 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.

Bluetooth earphones are a PAN

Suppose a student pairs a phone with wireless earphones and a smart watch while sitting at her desk.

Which type of network is this, and why?

Try it first, then show the solutionSolution

The devices are all within a few metres around one person.
The network is personal, short range and set up by the owner.

Answer: A PAN (Personal Area Network).

Memory hook: Personal means around one person.

A star lab

Suppose a school lab connects 12 computers by separate cables to one switch, and one computer's cable is cut.

What happens to the other computers, and what is the one weak point?

Try it first, then show the solutionSolution

In a star network each node has its own link, so the cut affects only that computer.
The weak point is the central switch: if it fails, no one can communicate.

Answer: Others keep working; the central switch is the weak point.

Memory hook: A star: if one arm breaks, only that arm goes dark.

Tricks to remember Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree

Short memory aids. Say each one aloud once, then use it on a question the same day.

PAN-LAN-MAN-WAN = Person-Local-Metro-Wide
The first letters give the order from smallest area to largest.
Use it when: Ordering network types.
Bus has a backbone, star has a centre, tree has branches
Key structural word for each topology.
Use it when: Naming a topology from a description.
Star: one arm breaks, others work
Star is the fault-tolerant layout for nodes; the centre is the weak point.
Use it when: Advantage and disadvantage of star.
Server where the crowd is
Place the server in the building with the most computers.
Use it when: Network design case.

Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: MAN · 1 mark · MCQBoard level

A network that covers a city and connects several LANs is called a:
(a) PAN (b) LAN (c) MAN (d) WAN

Try it first, then show the solutionSolution

A city-wide network is metropolitan.

Answer: (c) MAN

Example 2: Define PAN · 2 marks · Short answerBoard level

What is a PAN? Give one example.

Try it first, then show the solutionSolution

A Personal Area Network connects devices within the reach of one person, usually a few metres. (1 mark)
Example: a phone connected to wireless earphones over Bluetooth. (1 mark)

Answer: A network of personal devices around one person, such as phone and Bluetooth earphones.

Example 3: LAN versus WAN · 3 marks · Short answerHarder board level

Differentiate between a LAN and a WAN on three points.

Try it first, then show the solutionSolution

Area: LAN covers a building or campus; WAN covers countries or the world. (1 mark)
Speed and ownership: LAN is fast and owned by one organisation; WAN uses public or leased links and is slower. (1 mark)
Cost: a LAN is cheaper to set up and maintain; a WAN is costlier. (1 mark)

Answer: LAN is local, fast and low cost; WAN is wide-area, slower and costlier.

Example 4: Bus versus star · 3 marks · Short answerHarder board level

Compare the bus and star topologies by stating a merit and a demerit of each.

Try it first, then show the solutionSolution

Bus advantage: needs little cable and is cheap. (0.75 mark)
Bus disadvantage: a break in the backbone cable stops the whole network. (0.75 mark)
Star advantage: failure of one node or its cable does not affect other nodes. (0.75 mark)
Star disadvantage: if the central switch fails, the whole network fails. (0.75 mark)

Answer: As above (one advantage and one disadvantage of each).

Example 5: Case: campus design · 5 marks · Case-basedHOTS / competency

Suppose a college has four buildings: ADMIN, SCIENCE, LIBRARY and HOSTEL. Distances: ADMIN to SCIENCE 40 m, ADMIN to LIBRARY 60 m, SCIENCE to LIBRARY 50 m, LIBRARY to HOSTEL 90 m, ADMIN to HOSTEL 120 m, SCIENCE to HOSTEL 130 m. Computers: ADMIN 30, SCIENCE 70, LIBRARY 20, HOSTEL 50. (Assumption: a repeater is needed on a link longer than 100 m.)
(i) Which building should host the server? (1 mark)
(ii) Suggest a cable layout. (1 mark)
(iii) Is a repeater needed in your layout? (1 mark)
(iv) Which topology suits inside each building? (1 mark)
(v) Name the device to be placed in every building. (1 mark)

Try it first, then show the solutionSolution

(i) SCIENCE, because it has the most computers (70), so most traffic stays local.
(ii) SCIENCE to ADMIN (40 m), SCIENCE to LIBRARY (50 m) and LIBRARY to HOSTEL (90 m). All three links are shorter than 100 m.
(iii) No repeater is required, because no cable in the layout exceeds 100 m. (Linking ADMIN to HOSTEL directly, 120 m, would need one.)
(iv) A star topology, as all computers connect to one switch and a fault in one computer does not affect the others.
(v) A switch in every building.

Answer: (i) SCIENCE (ii) SCIENCE-ADMIN, SCIENCE-LIBRARY, LIBRARY-HOSTEL (iii) No (iv) Star (v) Switch

Where students lose marks in Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree

The slips examiners see most often, and what to write instead.

Mistake: Calling Bluetooth earphones a LAN
A LAN covers a building or campus; devices around one person form a PAN.
Wrong working
LAN
Right working
PAN
Do this: Look at the distance and ownership in the question.
Usually costs: 1 mark
Mistake: Claiming that star topology never fails
The central device is a single point of failure.
Wrong working
Star is fully fault-proof.
Right working
A node failure is isolated, but if the central switch fails the whole network fails.
Do this: Give both the strength and the weakness.
Usually costs: 1 mark
Mistake: Placing the server in the farthest building
The server should be near the largest number of computers to reduce traffic.
Wrong working
Server in HOSTEL because it is farthest.
Right working
Server in SCIENCE (70 computers).
Do this: Compare the computer counts before choosing.
Usually costs: 1 mark

Exam tips

Write PAN, LAN, MAN, WAN with full forms where asked.
Tie each advantage or disadvantage to a cause: single cable, central switch, backbone.
In network-design questions use the distance limit stated in the question, never one from memory.
Mesh and ring are in the NCERT book but outside the CBSE list; stick to bus, star and tree.
Mention the switch as the central device of a star.

Practice questions on Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree

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 topology in which every node connects to one central device is:
(a) bus (b) star (c) tree (d) ring
Hint
Central switch.
Answer
(b) star
Q2 · 1 mark · Very short answerBoard level
Name the topology that uses a single backbone cable with terminators at both ends.
Hint
Think of a bus line.
Answer
Bus topology.
Q3 · 3 marks · Short answerHarder board level
Describe the tree topology with one advantage and one disadvantage.
Hint
Think of star groups on a backbone.
Answer
A tree topology connects several star networks to a common backbone in a hierarchy. Advantage: easy to extend, each group can be managed separately. Disadvantage: the backbone or a top-level device failing cuts the groups off; it needs more cable and devices.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): In a star network, failure of the central switch stops all communication.
Reason (R): In a star network all nodes communicate through the central device.
(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
All traffic passes through the centre.
Answer
(a) Both are true and R explains A.
Q5 · 3 marks · Short answerHOTS / competency
Suppose a coaching centre has 3 branches in one city, each with a LAN of 20 computers, and wants to join them. Name the type of network formed, the topology to use inside each branch and one device for each branch.
Hint
City-wide joins LANs.
Answer
The joined network is a MAN. Inside each branch use a star topology. A switch (for the LAN) and a router (to link the branch to the others) are placed in each branch.

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.Which network covers a city?Show answer
MAN.
2.Which network is the Internet an example of?Show answer
WAN.
3.What is the common cable of a bus topology called?Show answer
The backbone.
4.What is the weak point of a star network?Show answer
The central switch or hub.
5.Which topology joins star networks to a backbone?Show answer
Tree.
6.Where is the server placed in a campus design?Show answer
In the building with the most computers.

Network Types and Topologies: PAN, LAN, MAN, WAN, Bus, Star, Tree: frequently asked questions

What is the difference between LAN, MAN and WAN?

A LAN spans a room, building or campus; a MAN spans a city; a WAN spans countries or the world. The area, speed and cost rise from LAN to WAN.

Which topology is the best for a school lab?

A star topology is common: every computer connects to a central switch, a fault in one computer does not stop the others, and adding computers is easy.

Are ring and mesh topologies asked in the CBSE paper?

The syllabus lists bus, star and tree only. Mesh and ring appear in the NCERT book but are outside the CBSE list.

How do I decide where to put a repeater?

Use the distance limit given in the question. If a cable in your layout is longer than that limit, place a repeater on it; otherwise state that none is needed.