Subnetting

In this article we will learn about subnetting   (sub + netting) in which sub means division and netting means network i.e. division of network. Subnetting is a process of division of large network into smaller networks.Here we will learn about subnetting of Class A , Class B. and Class C of  IPV4 ((Internet Protocol Version)

subnetting

Why subnetting is important ?
  1. To increase Network performance, it allows data to reach its destination faster.
  2. To allow limited number of users , this will provide security.

Example: If you have a group of friends and you have to use WiFi for internet purpose like in  a  hostel then you can allow limited number of users so that no extra person can have access to your WiFi device.

3. It allows organization of resources means if a company have several departments like sales ,             executive , finance etc. , it will be managed over a large network using subnetting.

Characteristics of Network :
  1. Number of subnets /networks (x) : It is division of large network into number of subnets or number of networks .It tells about number  of networks available after subnetting.
  2. Number of hosts per  subnet /network(y) : It tells us about total number of hosts/users in a network excluding network adddress and broadcast address.
  3. Block size (z) : It tells us  about the size of subnet including network address , host address and broadcast address. It is also defined as difference between two subnets.
Subnetting for Class C :

Let us take an IP address of Class C for subnetting  = 192.168.1.1 /26

We know that Default network bits for class C = 24 and it’s default subnet mask = 255.255.255.0

In binary = 11111111.11111111.11111111.00000000

According to our question there are 26 network bits, so new subnet mask = 255.255.255.192

In binary =  11111111.11111111.11111111.11000000

subnetting of class C

x = number of borrow bits

y = number of off bits

z = number of off bits in the octet where change is taking place

                                                 0 = off bit

                                                 1 = on bit

Number of subnets/ networks = 2x  = 22 = 4

Number of hosts per  subnet /network = 2y − 2 = 26 − 2 = 64−2 = 62

Block size = 2z = 26  = 64

 

 Network Address            first IP               Last IP      Broadcast Address
 192.168.1.0  192.168.1.1   192.168.1.62   192.168.1.63
 192.168.1.64   192.168.1.65   192.168.1.126   192.168.1.127
 192.168.1.128   192.168.1.129   192.168.1.190   192.168.1.191
 192.168.1.192   192.168.1.193   192.168.1.254   192.168.1.255

 

Subnetting for Class B :

Let us take an IP address of Class B for subnetting  = 172.24.0.1  /18

We know that Default network bits for class B = 16 and it’s default subnet mask = 255.255.0.0

In binary = 11111111.11111111.00000000.00000000

According to our question there are 18 network bits, so new subnet mask = 255.255.192.0

In binary =  11111111.11111111.11000000.00000000

subnetting of class B

x = number of borrow bits

y = number of off bits

z = number of off bits in the octet where change is taking place

                                                 0 = off bit

                                                 1 = on bit

Number of subnets/ networks = 2x  = 22 = 4

Number of hosts per  subnet /network = 2y − 2 = 214 − 2 = 16384−2 = 16382

Block size = 2z = 26  = 64

 Network Address            first  IP            Last  IP    Broadcast  Address
 172.24.0.0  172.24.0.1   172.24.63.254  172.24.63.255
  172.24.64.0   172.24.64.1  172.24.127.254  172.24.127.255
 172.24.128.0  172.24.128.1  172.24.191.254  172.24.191.255
 172.24.192.0  172.24.192.1  172.24.255.254  172.24.255.255

 

Subnetting for Class A :

Let us take an IP address of Class A for subnetting  = 2.2.2.2 /11

We know that Default network bits for class A = 8 and it’s default subnet mask = 255.0.0.0

In binary = 11111111.00000000.00000000.00000000

According to our question there are 11 network bits, so new subnet mask = 255.224.0.0

In binary =  11111111.11100000.00000000.00000000

subnetting of class A

 

x = number of borrow bits

y = number of off bits

z = number of off bits in the octet where change is taking place

                                                 0 = off bit

                                                 1 = on bit

Number of subnets/ networks = 2x  = 23  = 8

 

Number of hosts per  subnet /network = 2y − 2 = 221   − 2 = 16384−2 = 2097150

Block size = 2z    =25 = 32

 Network Address          first  IP         Last  IP    Broadcast  Address
 2.0.0.0   2.0.0.1   2.31.255.254  2.31.255.255
  2.32.0.0   2.32.0.1   2.63.255.254   2.63.255.255
 2.64.0.0  2.64.0.1   2.95.255.254  2.95.255.255
 2.96.0.0  2.96.0.1   2.127.255.254  2.127.255.255
 2.128.0.0  2.128.0.1   2.159.255.254  2.159.255.255
 2.160.0.0  2.160.0.1   2.191.255.254  2.191.255.255
 2.192.0.0  2.192.0.1  2.223.255.254  2.223.255.255
 2.224.0.0  2.224.0.1   2.255.255.254  2.255.255.255

 

 
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