Lets Learn "Network subnetting ( with examples )"

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In this tutorial, we'll be learning about the network subnetting as in what it is, why it is required, etc. 

What is subnet?

Basically, a subnet is derived from subnetWORK which means a logical subdivision of the IP network. A subnet is a network inside a network. Subnets make the network routing much more efficient.

Why subnetting is required?

1. It improves network performance and speed.

Some network protocols required broadcasting the network packets. If there are large number of devices, it means broadcasted packets need to reach more number of devices which can affect network switching performance and hence overall network performace.
With the help of subnetting, the broadcast domain is reduced and the packet need to be broadcasted only to the devices that are part of same subnet. Because now we are no longer spamming all the devices, it will increase the network switching performance and hence improves overall network perfomance.

2. It boosts network security.

Subnetting also boosts the network security. It might be possible that we don't wanna allow all the devices to access. Subnetting will help put such devices in different subnets and have a router with rules to restrict some kind of packets flow between the devices in different subnets using ACLs, which increases the network security.

3. It reduces network congestion.

This is similar to point 1. Since with subnetting the broadcast domain will be shortened which results in less spamming and hence less network congestion.

4. It controls network growth.

More the size of network, more difficult it is to manage it. Size is a very important factor while designing any network. One of the key benefits of subnet is that is controls the network size. We'll learn about how to calculate the network size later in this tutorial.

5. It makes network administration easy.

As we discussed, subnetting helps to control the network size. So lesser the the size, easy the network to manage. So subnetting helps admins a lot to manage the network. Admins always consider subnetting while designing any network.

Network and Host part in IP Address

IPv4 addresses are composed of two parts
  1. Network part: The first few numbers in the IP Address specify the network. All the IP Addresses with the same network part are part of the same network.
  2. Host part: The later numbers ( apart from the network part ) in the IP Address specify the host.
A subnet mask specifies which is the network part and which part is the host part.

For IP Address 172.54.123.76, and subnet mask 255.255.0.0 ( /16 ), The network and host part looks like the image below.

Calculation of network size from the subnet mask

If the subnet mask is /X, then the network size for the IPv4 network is.


IP Address classes

Let's learn about the IP Address classes. TCP/IP defined five classes of IP Address, each class has a range of valid IP Addresses. The value of first octet defines the class of the IP Address. The five classes include A, B, C, D & E. The first three classes IP Addresses are used for host addresses. The other classes server special purpose like class D for multicast and class E is for experimental purpose.

The system of IP Address classes was developed for the purpose of internal IP addresses assignment. The classes created were based on the network size. For example, for the small number of networks with large network size, class A was created. The class C was created for large number of small size networks.


Class

First Octet value

Subnet Mask

A

0-127

/8

B

128-191

/16

C

192-223

/24

D

224-239

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E

240-255

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Few examples

  1. 10.23.54.23 - This IP Address is a part of Class A. All the IP addresses that are in the form of 10.*.*.* ( where * is any number between 0-255 ) are part of the same network.
  2. 172.20.29.234 - This IP Address is part of Class B. All the IP addresses that are in the form of 172.20.*.* ( where * is any number between 0-255 ) are part of the same network. But 172.54.32.123 is not a part of the same network.
  3. 201.23.43.54 - This IP Address is part of Class C. All the IP addresses that are in form of 201.23.43.* ( where * is any number between 0-255 ) are part of the same network. 
  4. 235.23.45.45 - This IP Address is part of Class D.
  5. 252.43.23.45 - This IP Address is a part of Class E.

HOPE YOU LIKE THIS TUTORIAL. FEEL FREE TO COMMENT BELOW IF YOU HAVE ANY DOUBTS. AND STAY TUNED FOR MORE TUTORIALS :)

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