What is Subnetting?

In this blog, you are going to read about the subnetting, Examples, Advantages, and Disadvantages, and other information related to this article, so stay on this site for further information.


Subnetting is a method in which a large Internetwork is divided into two or smaller logical networks. These small groups of networks are called subnetworks or subnets.

These subnetworks or subnets have their own different network addresses. The subnet mask is used to create these small internetworks.

The subnet mask is used to differentiate between the network address and the host address in the IP address.
The subnet mask has only one main purpose, it identifies which part of the IP address is the network address and which part is the host address.


why use subnetting?

The need for subnetting arose because when the Internet became popular, all network IP addresses were being consumed. That is, there was a shortage of IP address at that time. Due to which the future of the World Wide Internet was in danger and it would have ended. To avoid this problem, subnetting was used., was created.

Advantage of subnetting 

  • The security system of this network is better because we can manage each subnet easily.
  • Due to the small network, the collision domain and broadcast domain also become small. Due to this the problem of traffic and breakdown is greatly reduced.
  • In this network, administrative control is better because a smaller network is easier to manage and administer as compared to a large network.
  • In subnet internet, networks are very helpful in solving the problem of IP addresses.
  • Subnets minimizes the size of routing tables in the Internet.

Disadvantage of subnetting

  • It is very expensive because it uses all the network devices like routers, switches, hubs, bridges, etc. which are very expensive.
  • Experienced administrative is required to manage this network.

What are the classes of subnetworks?

There are five classes of subnetworks:

Class A, Class B, Class C, Class D, and Class E.  Each class relates to a specific range of network IP addresses. Classes A, B, and C are used the most often by different networks.

Subnet classes are made unique by the number of bits their network IP addresses have dedicated to a network and the number of bits dedicated to hosts.  They each have a default subnet mask. Classes can be identified by the number in the first octet of their address.

  • Class A: First Octet Value 0-126
  • Class B: First Octet Value 128-191
  • Class C: First Octet Value 192-233
  • Class D: First Octet Value 224-239
  • Class E: First Octet Value 240-255

127 is not accounted for because it denotes a loopback address.

Create subnets

There are the following ways to create a subnet. In this article, we will subnet a Class C network address, which by default has 24 subnet bits and 8 host bits.

What we need to know before we start subnetting;

  • How many subnets do we need?

2x = number of subnets. x is the number of 1s in the subnet mask. With 1 subnet bit, we can have 21 or 2 subnets. 2 bits, with 22 or 4 subnets, with 3 bits, 23 or 8 subnets, etc.

  • How many hosts do we need per subnet?

2y – 2 = Number of hosts per subnet. y is the number of 0s in the subnet mask.

Subnetting example;

An example will help you to understand the subnetting concept. Suppose we need to subnet a class C network address We will need two subnets with 50 hosts per subnet. Here is our calculation:

  • Since we only need two subnets, we need 21 subnet bits. In our case, that means we’ll take one bit from the host part.:

First, we have a Class C address with a subnet mask of 24. Let’s convert them to binary: = 11000000.10101000.00000000.00000000 = 11111111.11111111.11111111.00000000

We need to take a zero from the host part of the subnet mask. Here is our new subnet mask: = 11111111.111111111.11111111.10000000

Remember, subnets represent networks with masks.

  • We need 50 hosts per subnet. Since we have taken one bit from the host part, we have seven bits left for the hosts. Is this enough for 50 hosts? The formula to calculate the number of hosts is 2y – 2, with y representing the number of host bits. Since 27 – 2 is 126, we have more than enough bits for our hosts.
  • Our network will look like this: – The subnet number of the first subnet is The IP address range in this subnet is – – The subnet number of the second subnet is The range of IP addresses in this subnet is –

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