Master IPv4, Subnetting & CIDR Complete Tutorial with Examples | ICT Networking Notes for Students

Complete IPv4, Subnetting & CIDR Tutorial

Master IP Addressing, Subnetting & CIDR with Examples, Tables, Exam Questions & High Scoring Notes

IPv4 Subnetting CIDR Networking ICT Revision

📘 Topics Covered

• IP Address
• IPv4 Classes
• Public & Private IPs
• Advantages & Disadvantages
• Subnetting
• /25 Subnetting
• /26 Subnetting
• /27 Subnetting
• Network & Broadcast IP
• CIDR
• CIDR vs Subnetting
• Exam Questions
• High Scoring Tips

1. What is an IP Address?

An IP Address (Internet Protocol Address) is a unique numerical address assigned to every device connected to a network.

Purpose of IP Address

• Identify devices on a network
• Enable communication between devices
• Send and receive data packets

Example of IPv4 Address

192.168.1.10

Structure of IPv4 Address

Octet	Binary Value
192	11000000
168	10101000
1	00000001
10	00001010

Exam Tip: IPv4 uses 32 bits divided into 4 octets.

2. IPv4 Classes

Class A

Feature	Details
Range	1 – 126
Subnet Mask	255.0.0.0
Network Bits	8
Host Bits	24

Class A IP Range

1.0.0.0 to 126.255.255.255

Private IP Range

10.0.0.0 – 10.255.255.255

Advantages

• Supports many hosts
• Suitable for large organizations

Disadvantages

• Wastes IP addresses
• Limited number of networks

Example

• ISP Network

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Class B

Feature	Details
Range	128 – 191
Subnet Mask	255.255.0.0
Network Bits	16
Host Bits	16

Private IP Range

172.16.0.0 – 172.31.255.255

Advantages

• Balanced network size
• Good for medium organizations

Disadvantages

• Can still waste addresses

Example

• University Network

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Class C

Feature	Details
Range	192 – 223
Subnet Mask	255.255.255.0
Network Bits	24
Host Bits	8

Private IP Range

192.168.0.0 – 192.168.255.255

Advantages

• Efficient for small networks
• Less wastage

Disadvantages

• Supports fewer hosts

Example

• School Computer Lab

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Class D

224.0.0.0 – 239.255.255.255

Used for multicast communication.

Class E

240.0.0.0 – 255.255.255.255

Used for research and experiments.

3. Public vs Private IP Addresses

Public IP	Private IP
Used on internet	Used inside local networks
Globally unique	Can be reused
Assigned by ISP	Assigned locally

Question: What is the difference between public and private IP addresses?

Answer: Public IPs are used on the internet and are globally unique while private IPs are used within local networks and can be reused.

4. Subnetting

Subnetting is the process of dividing a network into smaller subnetworks.

Advantages of Subnetting

• Better network management
• Improves security
• Reduces congestion
• Efficient IP usage

Disadvantages

• Complex configuration
• Requires planning

Important Terms

Term	Meaning
Network Address	First IP of subnet
Broadcast Address	Last IP of subnet
Usable Hosts	IPs assignable to devices
Subnet Mask	Defines network and host bits

5. Example: 192.168.5.0/25

Subnet Mask

255.255.255.128

Total IPs

128 IPs

Usable Hosts

126 Hosts

Subnet	Network IP	First Host	Last Host	Broadcast
Subnet 1	192.168.5.0	192.168.5.1	192.168.5.126	192.168.5.127
Subnet 2	192.168.5.128	192.168.5.129	192.168.5.254	192.168.5.255

6. Example: 192.168.5.0/26

Subnet Mask

255.255.255.192

Total IPs

64 IPs

Usable Hosts

62 Hosts

Subnet	Network IP	First Host	Last Host	Broadcast
1	192.168.5.0	192.168.5.1	192.168.5.62	192.168.5.63
2	192.168.5.64	192.168.5.65	192.168.5.126	192.168.5.127
3	192.168.5.128	192.168.5.129	192.168.5.190	192.168.5.191
4	192.168.5.192	192.168.5.193	192.168.5.254	192.168.5.255

7. Example: 192.168.6.0/27

Subnet Mask

255.255.255.224

Total IPs

32 IPs

Usable Hosts

30 Hosts

Subnet	Network IP	First Host	Last Host	Broadcast
1	192.168.6.0	192.168.6.1	192.168.6.30	192.168.6.31
2	192.168.6.32	192.168.6.33	192.168.6.62	192.168.6.63
3	192.168.6.64	192.168.6.65	192.168.6.94	192.168.6.95
4	192.168.6.96	192.168.6.97	192.168.6.126	192.168.6.127
5	192.168.6.128	192.168.6.129	192.168.6.158	192.168.6.159
6	192.168.6.160	192.168.6.161	192.168.6.190	192.168.6.191
7	192.168.6.192	192.168.6.193	192.168.6.222	192.168.6.223
8	192.168.6.224	192.168.6.225	192.168.6.254	192.168.6.255

8. CIDR (Classless Inter-Domain Routing)

CIDR is a method of allocating IP addresses efficiently without fixed classes.

Example of CIDR Notation

192.168.1.0/24

Advantages of CIDR

• Efficient IP allocation
• Reduces IP wastage
• Smaller routing tables
• Flexible network design

Disadvantages

• More difficult to understand
• Requires subnetting knowledge

How CIDR Works

• Uses variable-length subnet masks
• Allows flexible network sizes
• Improves routing efficiency

9. CIDR vs Subnetting

CIDR	Subnetting
Flexible allocation	Divides networks
Used mainly by ISPs	Used in organizations
Reduces routing table size	Improves network management
Does not depend on classes	Usually based on classes

Clear Difference

Subnetting divides one large network into smaller subnetworks while CIDR combines networks and allows flexible IP allocation.

Subnetting Example

192.168.1.0/24 → multiple /26 networks

CIDR Example

192.168.0.0/16

10. Common Exam Questions & Answers

Question: What is subnetting?

Answer: Subnetting is the process of dividing a network into smaller subnetworks.

Question: What is the subnet mask for /27?

Answer:

255.255.255.224

Question: How many usable hosts are available in /26?

Answer:

62 usable hosts

🔥 High Scoring Exam Tips

• Memorize subnet masks
• Practice block size calculations
• Always identify network and broadcast IPs
• Use tables for subnet answers
• Write formulas step-by-step
• Learn CIDR notation carefully

Common Student Mistakes

• Using broadcast IP as host IP
• Wrong subnet mask calculations
• Forgetting network address
• Incorrect block size calculations

Golden Rule: Students who show subnet calculations clearly with tables, formulas and proper IP ranges usually score the highest marks in networking questions.

Complete IPv4 & Subnetting Revision Notes

Study Smart • Practice Subnetting • Score High Marks in ICT Exams