Classes of IP Address

IP addresses can be classified into five categories which are the followings:

Class	Range
Class A	1	-	127
Class B	128	-	191
Class C	192	-	239
Class D	240	-	247
Class E	248	-	255

Note:

• Here, Range means of Network IDs (First Octet)
• Network 127 is reserved for loopback and internal testing.
• Class D address is reserved for Multicast.
• Class E address is reserved for experimental, used for research.

Each IP address field has two parts:

1. Network
2. Host

For Class A, the first 8 bits are used for Network and the other 24 bits are used for hosts. For Class B, the first 16 bits are used for Network and the other 16 bits are used for hosts. And for Class C, the first 24 bits are used for Network and the other 8 bits are used for hosts.

Remember, the first octet bits (the first 8 bits of each block of IP address) are used to determine the address class. Using the network bits, you can create many networks and the hosts bits are used to define each hosts of those network. The summary of number of subnets and no of hosts per subnet are defined below:

Class	No of Subnets	No of Hosts Per Subnet	Range of Network IDs
Class A	126	16,777,214	1-127
Class B	16,384	65,534	128-191
Class C	2,097,152	254	192-223