Network Security - Subnetting

Subnetting is a method used in computer networking to divide a large network into smaller, more manageable parts called subnets. Each subnet functions like a mini-network inside a bigger network.

What Subnetting Means

Imagine a big apartment building with hundreds of rooms. Instead of handling all rooms as one big block, the building is divided into floors.
Each floor is easier to manage and organize.

Similarly, subnetting divides a large IP network into smaller sections so that:

the network becomes easier to manage
network traffic stays organized
security improves
performance becomes better

Why Subnetting Is Important

Efficient IP Address Usage
Prevents wasting IP addresses by assigning only what each subnet needs.
Improves Network Performance
Reduces unnecessary traffic and keeps each subnet’s data local.
Enhances Security
Devices in one subnet can be isolated from another subnet if needed.
Better Network Management
Makes it easier to control and troubleshoot the network.

Key Concepts in Subnetting

1. IP Address

Example: 192.168.1.50
Contains network part + host part.

2. Subnet Mask

Example: 255.255.255.0
It tells how much of the IP address is the network portion.

3. Network Address

Identifies the subnet itself (e.g., 192.168.1.0).

4. Broadcast Address

Used to send data to all devices in the subnet
(e.g., 192.168.1.255).

5. Host Addresses

Usable IPs for devices inside that subnet.

How Subnetting Works (Easy Example)

Let’s say you have the network:
192.168.1.0 /24

This gives 256 total addresses.

But you want to divide it into 4 smaller networks.

You can create four subnets:

192.168.1.0 /26
192.168.1.64 /26
192.168.1.128 /26
192.168.1.192 /26

Each subnet now has:

64 addresses total
62 usable IPs

This helps organize different departments, floors, or teams in a company.

Real-Life Use of Subnetting

A company might create separate subnets for:

HR
Finance
IT
Guest WiFi

Each group gets its own subnet so performance improves and access is more secure.