CCNA Notes #01: Computer Networks — Types & Classification (Complete Guide)

Computer Networks — Types & Classification

A complete reference covering what a network is, how networks are classified, and the key types you need to know for CCNA — built from classroom notes, teacher explanations, and structured revision.

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1What is a Network & Networking?

What

A network is a group of two or more devices connected together so they can share information with each other. Networking is the purposeful process of setting up, using, maintaining, and troubleshooting those connections to make that sharing actually work.

Why

Without a network, every device is isolated — you'd have to physically transfer files, share printers one at a time, or duplicate data everywhere. Networking removes that friction and allows resources, services, and data to be shared efficiently.

Key terms to know

Intranet

Private, internal communication within an organization or domain

Internet

Public communication with the World Wide Web—open to everyone

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2How Networks Are Classified

Networks are grouped into three broad categories based on different criteria:

Category A

By host role

Category B

By geographical area

Category C

By participation

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AClassification by Host Role

This is about the role a device plays on the network — does it ask for services, provide them, or both?

Client

A device that requests services from another device. It cannot provide services to others.

Example: Your laptop requests a webpage from a web server. Your laptop is the client.

Server

A device that provides services to other devices. It responds to requests but does not initiate them.

Example: A web server hosts files and sends them to whoever requests them.

Peer-to-Peer (P2P)

Devices that can both request and respond to services at the same time. There is no central authority — every device is equal.

Example: Torrenting — your device downloads parts of a file from others while simultaneously sharing parts it already has.

Client-Server vs Peer-to-Peer — Quick comparison

Feature	Client-Server	Peer-to-Peer
Data storage	Centralized on server	Distributed across peers
Visibility	Clients can't see other clients	Every peer knows who else is connected
Data access	Client fetches from server directly	Peer needs another peer to download data
Failure risk	Single point of failure (server down = all down)	No single point—others stay accessible
Use case	Websites, email, banking systems	File sharing (BitTorrent), blockchain

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BClassification by Geographical Area

This is the most important classification for CCNA. Networks are grouped by how much physical area they cover.

PAN

Personal Area Network

Range: ~1–10 metres

A network for your personal devices in immediate proximity. The smallest type of network.

BluetoothMobile hotspotPersonal Wi-Fi

LAN

Local Area Network

Range: Room → Building (<1 km)

Covers a small area like an office, floor, or building. High-speed, privately owned, uses Ethernet (UTP cables + switches).

Office networkHome Wi-FiSchool lab

CAN

Campus Area Network

Range: Multiple buildings / a few km

Think of it as a bigger LAN connecting multiple buildings in one campus. It is NOT a rename — it is a scale-up of LAN.

University campusCorporate HQAirport

MAN

Metropolitan Area Network

Range: City / metropolitan area

Larger than CAN/LAN but smaller than WAN. Covers an entire city. Formed by connecting multiple LANs.

City-wide ISPCable TV network

WAN

Wide Area Network

Range: Countries / continents

The largest network type. Connects multiple LANs and MANs across huge distances. Uses both public and private links. Generally slower than LAN.

InternetBank branch network

SAN

Storage Area Network

Range: Data centre (dedicated)

A high-speed network built purely for connecting servers to storage devices. Not for general internet use—purpose-built for data centers.

Fibre ChanneliSCSIData centres

Quick size order to remember: PAN < LAN < CAN < MAN < WAN. SAN is separate — it's defined by purpose (storage), not size.

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CClassification by Participation (Access Type)

This classifies networks based on who is allowed to access them.

Private Network

• Access is restricted to authorized users only
• Data is protected and internal
• Example: Corporate internal network, school intranet

Public Network

• Open to all—authorized and unauthorized users alike
• Example: The internet, public Wi-Fi at a café

VPN — Virtual Private Network

What

A VPN is a logical private network built on top of a public network. It creates a secure encrypted tunnel between a client and a server over the internet — so it behaves like a private network even though the physical path is public.

Why

When you connect to a public network (like the internet), your data is visible and vulnerable. VPN encrypts that data and keeps it private — important for remote workers, branch offices, and anyone handling sensitive information.

How

VPN works by connecting physically through an ISP (Internet Service Provider) but logically through an encrypted tunnel. The tunnel ensures no one in between can read your data.

Your device

Sends encrypted data

Public internet (ISP)

Carries the tunnel

VPN Server

Decrypts and routes

Destination

Private network / resource

Examples

Remote employee accessing office filesBranch-to-branch site connectivitySecure browsing on public Wi-Fi

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✓Quick Revision Summary

Network	Full form	Coverage	Key point
PAN	Personal Area	1–10 m	Personal devices, Bluetooth
LAN	Local Area	Building / <1 km	Ethernet, privately owned, high speed
CAN	Campus Area	Multiple buildings	Bigger LAN, not a rename
MAN	Metropolitan Area	City	Multiple LANs joined together
WAN	Wide Area	Countries / continents	Connects LANs & MANs, internet is the biggest WAN
SAN	Storage Area	Data centre	Storage-specific, Fibre Channel / iSCSI
VPN	Virtual Private	Anywhere (logical)	Private network over public network, encrypted tunnel