In classful addressing, an IP address of class A,B and C is divided into two parts : netid and hostid. The netid and hostid are of varying lengths, depending on the class of the address. Netid: The part of an IP address that identifies the network. Hostid: The part of an IP address that identifies a host in a network. Class A: One byte netid three bytes host id Class B: Two bytes netid Two bytes host id Class C: Three bytes netid One byte host id Example: 1. IP address: 84.42.58.11 Binary Notation: 01010100 00101010 00111010 00001011 It is a class A IP address. The network address /netid is 84.0.0.0 The host addresses /hostid is 0.42.58.11 2. IP address: 144.62.12.9 It is a class B IP address. The network address /netid is 144.62.0.0 The host addresses /hostid is 0.0.12.9