Summery: In this article we are talking about IPv4 Subnetting.

IP subnetting is a method used to subdivide a network in to multiple networks. In this article let’s learn IP subnetting with 5 simple steps. So without further ado let’s get started.

Also Read: IP Addressing – Introduction and Classful Addressing

? There is a network with the IP 216.21.5.0 you need to subnet this network into 5 networks.

Step 01

First of all identify the Class of the IP address which belong to your network.

So according to the above chart IP address 216.21.5.0 belong to Class C. Because 216 belong to 192 – 223 range.

In the question they are saying us to subnet the network into 5 networks. So we need to find where does number 5 lies in the below number sequence.

Number 5 lies in between 8 and 4 according to the above number sequence. So if we draw a separator between 8 and 4 to denote number 5 we can see that there are 3 numbers in the right side of the separator.

Step 02

Find out the default Subnet Mask of Class C IP addresses (because the given IP is a class c IP address) from the first chart.

Default Subnet Mask = 255.255.255.0

Now we need to find out the new subnet mask. Our default subnet mask is 255.255.255.0 therefore we can only change the last octet.

In step 01 we saw that there are 3 numbers in the right side of the separator. In the new subnet mask we are using 1’s to denote those 3 numbers. (The question is about networks that’s why we are using 1’s to denote those 3 numbers. If the question is about hosts we need to denote those numbers using 0’s.)

Step 03

Now let’s find the increment.

Increment = 256 – 224 = 32

Step 04

Let’s calculate the number of networks.

No. of networks = 2^n = 2^3 = 8

Let’s Calculate the number of hosts per network.

No. of hosts per network = 2^n – 2 = 2^5 – 2 = 30

Step 05

Now we can easily find the Network/Subnet IDs, Network IPs and Broadcast IDs.

? There is a network with the IP 195.5.20.0 you need to subnet this network into 50 networks.

Step 01:

IP address 195.5.20.0 belong to class c. Therefore default subnet mask is 255.255.255.0

Step 02:

Default Subnet Mask = 255.255.255.0

New Subnet Mask = 11111111.11111111.11111111.11111100 = 255.255.255.252

Step 03:

Increment = 256 – 252 = 4

Step 04:

No. of Networks = 2^n = 2^6 = 64

No. of hosts per network = 2^n -2 = 2^2 – 2 = 2

Step 05:

? Subnet 200.1.1.0 into 40 hosts per network.

In these type of questions they are not telling us to find the networks. They are asking us to find the hosts per network. To solve these kind of question we can use the same steps as we did in above questions. But you need to do a little twist in this questions. Instead of using 1’s to denote those numbers in the right side of the seperator use 0’s to denote those numbers.

Step 01:

IP address 200.1.1.0 belong to class c. Therefore default subnet mask is 255.255.255.0

Step 02:

Default Subnet Mask = 255.255.255.0

New Subnet Mask = 11111111.11111111.11111111.11000000 = 255.255.255.192

Step 03:

Increment = 256 – 192 = 64

Step 04:

No. of Networks = 2^n = 2^2 = 4

No.of hosts per network = 2^n – 2 = 2^6 – 2 = 62

Step 05:


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