Subnetting in computer network & Advantages & Disadvantages

In today’s article, we will know Subnetting in computer network, why it is used, and Advantages & Disadvantages of subnetting. Many students get confused about what subnetting is and how it is made. So, in this article, with an example, we are going to provide you with the knowledge of subnetting in detail. This article must be read till the end so that you can get complete information about subnetting. So let’s start without delay.

What is Subnetting in Computer Network?

Simply dividing a large network into smaller parts is called subnetting. For example, in a large organization, it is a difficult task for one person to handle all the work. So, all the tasks are separated and the responsibility is given to a person who has the ability to do that work.

Similarly, managing a large network with a network administrator is a very difficult task. Therefore, the network is divided into small parts. So that, small networks can be easily managed.

Subnetting is a process that is done within a network. This is done to remove the difficulty of network management. We can make a network with multiple subnets according to our needs. So that small networks can be easily managed.

We use the IP address of 5 classes. There are many hosts in all the classes, due to which the wastage is also very high. Using subnetting reduces wastage.

If we talk about security, then in a big network it is difficult to authorize many hosts, give IP addresses and provide usernames and passwords to all of them. But by dividing the network into smaller parts, then the security of the network will be enhanced.

What is subnet mask?

The subnet mask is 32 bits. For this, it is easy to find the IP address in a network. Because of this, the computer that uses the IP address must have a subnet mask. Whenever a data packet enters a network, the router finds the particular IP address through the subnet mask and reaches the data packet in the right place.

Each IP class uses a different subnet mask.

Class Default subnet mask
Class A255.0.0.0
Class B255.255.0.0
Class C255.255.255.0

How Subnetting is done in networking

We can do subnetting in all the classes of IP addresses. But due to the large number of hosts in class A and class B, it will be difficult to describe them. So we will do subnetting with a Class C IP address.


There must have been a strong debate in your mind that what is a possible host and what is a usable host. And why is there 2 points less in the usable host? This means that the first host number of all classes is the network address and the last host is the broadcast address.

For example, class C has 256 host addresses and only 254 of them are used. Because its first host address is used in 0 – network address, and the last address is 255 – broadcast address. That’s why we use 254 no of host address.

How subnetting is done?

We take an IP address of class C.

Class C –

In this, we do not have to change anything in the first 3 octets. If you change it, then the whole network will change. Because in class C the first 3 octets are network ID.

Advantages & Disadvantages of subnetting

In the above image, how a network can be divided into two subnets has been told. Now in subnet 1, the host use will be 126 and in subnet 2 the host use will be 126.

There must be confusion in your mind that the network Id of S1 is the same as the network Id of the entire network. The broadcast ID of S2 is the same as that of your network. So there is nothing to be confused about in this. It depends on whether it is inside the network or outside the network. So if subnetting is done in a network then an internal router is used inside that network.

Subnetting in computer networks examples

For example, if a student is taking admission to a new college, first he will find the college where it is. After that, he will find his department inside the college building and go to it. Similarly, when a data packet comes towards the network, first it comes to the router which is installed before the network. The router extracts the destination IP address of that data packet and finds out what is its default mask. After that, the router sends that data packet to the router inside the network.

When the data packet reaches the internal router, how will that router know which subnet the data packet has to go to? So it would have been with the subnet mask. When subnetting a network, the router installed in the internal must be given a subnet mask. So that the router knows in which subnet to send the data packet.

Why do we use subnetting?

Earlier no one knew about the availability of the internet. Due to this very few people used the internet. As technology changed, the desire for the Internet also increased. When some people used to use the internet, then it was possible to give their IP addresses. But as the Internet increased, the number of IP addresses decreased. To shoot out this problem, a new technique like subnetting was introduced.

For this reason, subnetting is used in large organizations. Due to subnetting, large networks can be easily managed by dividing them into smaller parts. So, let’s get the knowledge about advantages & disadvantages of subnetting.

Advantages and Disadvantages of Subnetting

Advantages of subnetting

  • With the help of subnetting, we can create many hosts in a network, and it’s easy to manage.
  • By dividing a large network through subnetting, the security of the network is increased.
  • As the network becomes smaller, the collision domain and broadcast domain also become smaller. Due to this the problem of traffic and breakdown is reduced.
  • Due to subnetting, the small network is managed by the network administrator better than the big network.
  • The biggest advantage of subnetting is, we can divide a network into multiple parts and give maximum internet connections.

Disadvantages of subnetting

  • If you want to find a host in a network, first you have to find the network ID, then the IP address, and then the port number.
  • To find the host in a network, one has to find the network ID first, then the IP address, and then the port number. But using subnetting in the network increases one step. So it has to find the network ID first, then the subnet, then the IP address, and finally the port number and reach the host.


In today’s post, we have provided you with complete information about Subnetting in computer networks and the Advantages & Disadvantages of subnetting. I hope you must have understood about subnetting. If you have any doubts regarding subnetting or need some improvement in this post, then you can tell us by commenting in the comment box. We will definitely solve your problem.

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