Basic Subnetting in Computer Networks Explained

This tutorial explains basic concepts of Subnetting in Computer Networks with examples. Learn what Subnetting is and why we do Subnetting in computer networks along with advantages and disadvantages of Subnetting in detail.

What is Subnetting?

Subnetting is a process of dividing a single large network in multiple smaller networks. A single large network is just like a town without any sector and street address. In such a town, a postman may take 3 to 4 days in finding a single address. While if town is divided in sectors and streets, he can easily find any address in less than one hour.

subnetting example

Let’s take another example. Due to maintenance there is a scheduled power cut. If town is divided in sectors, electric department can make a local announcement for the affected sector rather than making an announcement for the whole town.

subnetting example broadcast message

Besides these two examples, you can take several other examples from real life where large objects are divided in smaller sections.

Computer networks also follow the same concept. In computer networking, Subnetting is used to divide a large IP network in smaller IP networks known as subnets.

A default class A, B and C network provides 16777214, 65534, 254 hosts respectively. Having so many hosts in a single network always creates several issues such as broadcast, collision, congestion, etc.

Let’s take a simple example. In a company there are four departments; sales, production, development and management. In each department there are 50 users. Company used a private class C IP network. Without any Subnetting, all computers will work in a single large network.

subnetting example a network without subnetting

Computers use broadcast messages to access and provide information in network. A broadcast message is an announcement message in computer network which is received by all hosts in network.

Earlier in this tutorial we discussed an example of electric announcement. You can relate that example with this example. In that example we learned how dividing a town in sectors can reduce announcement area.

In this example since all computers belong to same network, they will receive all broadcast messages regardless the broadcast messages which they are receiving are relevant to them or not.

Just like town is divided in sectors, this network can also be divided in subnets. Once network is divided in subnets, computers will receive only the broadcasts which belong to them.

Since company has four departments, it can divide its network in four subnets. Following figure shows same network after Subnetting.

subnetting example network after subnetting
Description Network 1 Network 2 Network 3 Network 4
Network address
valid hosts to to to to
Broadcast address

To learn how this chart is prepared or how Subnetting is done, please see the next part of this tutorial.

This tutorial is the second part of the article “Subnetting explained with examples”. Other parts of this tutorial are available here.

Network addressing basic concept explained

This is the first part of the article. It explains what IP address is and how IP address works in computer network including IP classes, subnet mask, private IP addresses, public IP addresses, reserved IP addresses, network address and broadcast address in detail.

Subnetting Explained with Example

This is the third part of the article. It explains methods and techniques of Subnetting which you need in learning and performing Subnetting in correct and easy way.

Advantage of Subnetting

  • Subnetting allows us to break a single large network in smaller networks. Small networks are easy to manage.
  • Subnetting reduces network traffic by allowing only the broadcast traffic which is relevant to the subnet.
  • By reducing unnecessary traffic, Subnetting improves overall performance of the network.
  • By blocking a subnet’ traffic in subnet, Subnetting increases security of the network.
  • Subnetting reduces the requirement of IP range.

Disadvantage of Subnetting

  • Different subnets need an intermediate device known as router to communicate with each other.
  • Since each subnet uses its own network address and broadcast address, more subnets mean more wastage of IP addresses.
  • Subnetting ads complexity in network. An experienced network administrator is required to manage the subnetted network.

That’s all for this introductory part. In next part we will learn how Subnetting is done step by step with practical examples. If you have any suggestion or comment about this tutorial, please mail me. If you like this tutorial, please don’t forget to share it with friends through your favorite social channel.

ComputerNetworkingNotes CCNA Study Guide Basic Subnetting in Computer Networks Explained