Classful network Introduction of address classes Introduction of address classes

| 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 |