What is Subnetting | Subnet Mask

what is subnetting

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As you have seen the IP address classes for the classes, we will see what is subnetting in this article. First of all we will see what is subnet mask.

What is Subnetting | Subnet Mask

The IP address consists of two parts. Host ID and Network ID. Depending upon IP address classes, network ID and host ID can be determined. This is because of the default subnet masks for the classes.

Let us see an example. Consider an IP address 10.0.0.1 now, in this address, we can see 10.0.0.0 is network id and 10.0.0.1 is host id Computer determines this by using the AND operation of IP address and subnet mask (in their binary format i.e. 0/1).

For classes, the default subnet masks are:

  • Class A: 255.0.0.0
  • Class B: 255.255.0.0
  • Class C: 255.255.255.0

Now we’ll see subnetting.

What Is Subnetting

Suppose we want to make different units inside the organization. That means we want to assign PCs 1-10 for one department and 11- 20 for others. Then we can use subnetting as it will reduce unnecessary traffic.

The device can broadcast to all the devices if the destination is unknown. And if we divide the network then it will surely reduce the useless traffic. Also, for security it will help as not every device will communicate with others.

Subnetting is basically diving a network into smaller networks. Let us see how to create subnets.

Firstly, remember that 2^x=N, N=number of subnets. x is the number of host bit to borrow to make the subnet.

And after borrowing the host bits, the number of hosts can be calculated as 2^remaining host bits -2 with those 2 being broadcast id and network id.

Consider the network 12.0.0.0 We will divide this into two subnets.

So, convert the address into binary. (as this is in class A, the three octets after the first are host part)

so, 0000 1100.0000 0000. 0000 0000. 0000 0000 – 12.0.0.0

Now we will borrow one host bit.

0000 1100.1000 0000. 0000 0000. 0000 0000 – 12.128.0.0

So the subnets are : 12.0.0.0 and 12.128.0.0

First IP address of each subnet is their network ID and last is broadcast ID. All others can be assigned as host IP addresses.

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