Classful network
Introduction of address classes
Columns: Class | Leading bits | Size of network number bit field | Size of rest bit field | Number of networks | Addresses per network | Start address | End address
Class A | 0 | 8 | 24 | 128 (2 7 ) | 16,777,216 (2 24 ) | 0.0.0.0 | 127.255.255.255 | Class B | 10 | 16 | 16 | 16,384 (2 14 ) | 65,536 (2 16 ) | 128.0.0.0 | 191.255.255.255 | Class C | 110 | 24 | 8 | 2,097,152 (2 21 ) | 256 (2 8 ) | 192.0.0.0 | 223.255.255.255 | Class D ( multicast ) | 1110 | not defined | not defined | not defined | not defined | 224.0.0.0 | 239.255.255.255 | Class E (reserved) | 1111 | not defined | not defined | not defined | not defined | 240.0.0.0 | 255.255.255.255