What Is IP Address Class?

An IP (Internet Protocol) address class represents a group of IP addresses assigned for a specific local network size.

Every IP address is really made up of two parts: a "network" part, which identifies a local network, and a "host" part which identifies a host within the local network.

Since local networks have different sizes, some are small and some are large, IP addresses are divided into 3 address classes.

1. Class A - Class A IP addresses are reserved for large local networks with up to approximately 16 million hosts. Each class A network is identified with the first decimal number in the range of "1" to "127". For example, IP address "1.4.3.2" is a class A address in a network identified as "1" and assigned to Asia Pacific Network Information Centre (APNIC).

2. Class B - Class B IP addresses are reserved for medium local networks with up to 65,536 hosts. Each class B network is identified with first 2 decimal numbers in the range of "128.0" to "191.255". For example, IP address "180.222.102.202" is a class B address in a network identified as "180.222" and assigned to Yahoo.

3. Class C - Class C IP addresses are reserved for small local networks with up to 255 hosts. Each class C network is identified with first 3 decimal numbers in the range of "192.0.0 to 223.255.255". For example, IP address "192.205.32.77" is a class C address in a network identified as "192.205.32" and assigned to AT&T.

Here is summary of IP Address Classes:

Class   Pattern           Network                 Example
A       nnn.***.***.***   1 - 127                 1.4.3.2
B       nnn.nnn.***.***   128.0 - 191.255         180.222.102.202
C       nnn.nnn.nnn.***   192.0.0 - 223.255.255   192.205.32.77

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