In order to provide the flexibility required supporting different size networks, the designers decided that the IP address space should be divided into 5 different address classes.
CLASS A NETWORKS (/8 PREFIXES): - Each class a network has an 8 bit network prefix with the highest order bit set to o and a seven bit network number, followed by a 24 bit host number. Today it is no longer considered modem to refer to a class a network. Class a networks are now referred it as “/85.A maximum of 126(27-2)/8 Networks can be defined. The calculation requires that the 2is subtracted because the /8 networks 0.0.0.0 is reserved for use as the default route & the /8 network 127.0.0.0 has been reserved for the loop back function.
CLASS B NETWORKS(1/6 PREFIXES): - Each class b network has a 16 bit network prefix with the two highest order bits set5 to 1-09 and a 14 bith network number followed bya 16 bit host number class b networks are now referred to as “/16s. Since they have 16 bit network prefix. A maximum of 16, 384(2 14)/16 networks can be defined with up to 65, 534(2 16 – 2) host per network. Since the entire /16 address block contains 2 30( 1, 073, 741, 824) addresses, it represents 25% of the total ip< 4
CLASS C NETWORKS( /24 PREFIXES):- Each class c network address has a 24 bit network prefix with the 3 highest order bits set to 1-1-0 and a 21 bit network number, followed by an 8 bit host number, class c networks are now referred to as “/24s since they have a 24 bit network prefix. A maximum of 2,097,152 (2 21)/24 networks can be defined with up to 254 (2 8 -2) hosts per network. Since the entire/ 24 address block contains 2 29 (536, 870, 912) address, it represents 12.5% of the total ipv4 uni-cast address space.
CLASS D NETWORKS: - These addresses have their leading four bits set to 1-1-1-0 and the remaining 28 bits are used to support IP multicasting.
CLASS E ADDRESS: - They has their leading 4 bits set to 1-1-1-1 and is reserved for experimental use or future use.