Network Segmentation & IP Subnetting: Definition & Processes

Instructor: Mario Giuffrida

Mario has a Master Degree in Computer Engineer and many years of experience in Java Programming

In this lesson, we will learn about what is Network Segmentation and why we need to segment a network. We will also discuss about how to achieve Network Segmentation using IP Subnetting.

A Congested Village

Suppose there is a little village with just a single road and all the houses are built overlooking the road, as represented in Figure 1. People in this village are happy and friendly, and have created their own groups of friends. Each group of friends distinguish themselves from the others by painting their front door with the same color. The village has 3 groups: the yellow friends, the red friends and the blue friends.

Figure 1: Village
Village with single road

The people in the village love to visit their friends' house frequently, however, driving between the houses is often a nightmare as the road is often congested (Figure 2). Furthermore, the red group of friends like to play spy and track every movement of the yellow group of friends. They can spy on them easily as the yellow group people often need to pass by the front doors of the people in the red group.

Figure 2: Congested Village
Village with single road and cars

What could be done to improve the villagers lives? How can we prevent spying and increase privacy of the people in the yellow group? How can we reduce the problem of traffic congestion?

The Solution

Imagine if we could split the main road into sections and dedicate each section to a group of friends, as shown in Figure 3.

Figure 3: Village with Dedicated Roads
village with multiple roads

With dedicated road sections, there will not be so many cars on the same road. Furthermore, with this solution, the people in the yellow group don't need to drive by the houses of the red group of people. Their privacy is thus protected.

In our solution in Figure 3, we have the following elements:

  • 3 sections of roads, uniquely identified by their road names (Yellow Street, Red Street, Blue Street).
  • Each road trunk has houses uniquely identified by their door number.

Computer networks present very similar issues to the ones we saw in the village example. Let's see how we can resolve these problems.

Segmenting Computer Networks

Network Congestion and Security represent two of the main problems experienced when using a single, big network trunk.

Network Segmentation and IP Subnetting help us to design better network topologies by splitting a computer network into smaller chunks, called subnets. Let's see how.

Network Segmentation is the process of dividing a network into multiple smaller networks (subnets/segments). IP Subnetting provides a way to uniquely define the subnet and the specific device address inside a computer network.

From Figure 1 to Figure 3 we have segmented the road. To understand how to do this in a computer network, we need to introduce the below terms:

IP Address, Subnet and Subnet Mask

The IP Address is the unique ID assigned to a host or an interface in a network. For example, your computer might have the IP address and your mobile phone Relating this to our example, it is similar to a complete house address, for example, 9 Red Street.

The Subnet is the trunk of a computer network. It is a smaller network within the bigger network. Subnets share the same address. For example, 192.168.0 is a subnet address. In our example, this matches to the road name, for example, Red Street.

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