IP Network Classes and Addresses

Each IP Network address is written as four parts separated by dots. Each of these parts comprises 8 binary bits. The 8 binary bit make an octet, so that each IP address has four octets. For example, the IP address is made up of 4 octets having the following binary bits:-

The IP addresses are grouped into classes. The classes are defined by the most significant four bits of the first octet. The tables below show a short form of the IP addresses and their classes.
Class First Octet First 4 Bits Remarks
A 1 - 127 0000  
B 128 - 191 1000  
C 192 - 223 1100  
D 224 - 239 1110 Multicast
E 240 - 255 1111  Experimental 

Loopback Testing
Class First 2 Octets Remarks
A 127.0 - 127.255  

Class IP Address CIDR Prefix
  A - /8
  B - /12
  C - /16



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(c) Compiled by B V Wood.

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