Class A addresses

In class A, the first octet (/8 prefix) is used to represent the network portion, and the remaining three octets are used to represent host addresses. It is obvious that in class A, the number of networks is noticeably smaller than the number of hosts per network. For that reason, class A is used to support mostly large organizations that prefer to have a small number of networks and a large number of hosts per network. The following table provides information about class A:

Class	Range	Maximum Number of Networks	Number of Hosts per Network	Leftmost Bit
A	`0.0.0.0`* - `127.255.255.255`**	2⁷= 128	2²⁴ - 2 = 16,777,214	0

* According to the Internet Engineering Task Force (IETF), the IP address 0.0.0.0 is a reserved address for this host on this network.

** IP addresses from 127.0.0.1 to 127.255.255.255 are reserved for loopback purposes and diagnostic functions.