How to Subnet (IP network)

Dear reader, This post may be childish to you if you have some knowledge in IP networking. But for a mystery user like me fall in different problems several time due to lack of IP addressing practice. So, I tried to make it a common source for my close friends.

IP Class:
Class A
Leading Bit Pattern : 0xxxxxxx
First Octet in Decimal: 0–127
Note: 0 is invalid;127 reserved for loopback testing

Class B

Leading Bit Pattern : 10xxxxxx
First Octet in Decimal: 128–191

Class C

Leading Bit Pattern : 110xxxxx
First Octet in Decimal: 192–223


Class D

Leading Bit Pattern : 1110xxxx
First Octet in Decimal: 224–239
Note: Reserved for multicasting


Class E

Leading Bit Pattern : 1111xxxx
First Octet in Decimal: 240–255
Note: Reserved for future use / testing
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Class A:  NHHH
Class B: NNHH
Class C: NNNH
Formula :
(Where N is equal to number of bits borrowed;
Where Where H is equal to number of host bit)
2(to the power) N = Number of total subnet created

2(to the power)N– 2 =  Number of valid subnets created

2(to the power)H = Number of total hosts per subnet
2(to the power)H– 2 = Number of valid hosts per subnet