In computer networking, a broadcast domain allows devices to discover and communicate with each other. As that domain grows, more hosts generate more broadcasts, which can slow the network down.
Subnetting gives you a way to divide a large network into smaller, more manageable pieces. In this module, you will see how subnetting works in practice and where it fits into real network designs.
"Good subnetting is like good city planning - clear boundaries, less congestion and easier routes for everyone."
🔎 What you will learn
- 🌐 How subnetting breaks a large broadcast domain into smaller subnets
- 🏢 Ways to subnet by location, department or device type
- 🔢 How prefix lengths like /8, /16 and /24 relate to traditional network classes
- 🧮 Why careful subnetting reduces wasted IP addresses and noisy network traffic
🧠 What is subnetting?
Subnetting is the process of dividing a large broadcast domain into smaller ones, known as subnets. This is done by borrowing host bits from the IP address to create subnet bits.
Smaller subnets reduce broadcast traffic and help you organise devices logically, which leads to better performance and easier troubleshooting.
⚙️ Advantages of subnetting
- 📉 Reduces network-wide broadcast traffic
- 🚀 Improves performance and responsiveness
- 🔐 Enhances security through logical segmentation
- 📋 Supports cleaner IP address planning
🏢 Subnetting by location
One common approach is to design subnets around physical locations, such as different floors in a building or different offices.
Example: Floor 1 - 10.0.1.0/24 where usable host addresses start at 10.0.1.1, 10.0.1.2, and so on.
🏛️ Subnetting by org units or device type
You can also align subnets with organisational units (for example HR, Students, Admin) or with device types such as printers, servers or IoT devices. This makes it easier to apply targeted policies and access controls.
🔢 Prefix changes and legacy network classes
Prefix lengths describe how many bits of the IP address are used for the network portion. Historically, these mapped to classes:
/8- often referred to as Class A/16- often referred to as Class B/24- often referred to as Class C
✅ Key takeaway
Efficient subnetting reduces wasted IP addresses, limits broadcast traffic and gives you cleaner logical boundaries for securing and managing your network.
