The IP ranges as specified A,B,C,D makes one ask why they are in those ranges,
actually the answer is pretty straight forward if we convert them into bits, you can start seeing the pattern,
after all the computers use IP more than we do, and since they think binary, then its binary that counts
Class A
Decimal : 0.0.0.0 - 127.255.255.255
Binary : 0000 0000.0000 0000.0000 0000.0000 0000 - 0111 1111.1111 1111.1111 1111.1111 1111
As you can see the first bit from the left stays 0 while the rest of the bits increments (bit by bit)
up to all ones.
Class B
Decimal : 128.0.0.0 - 191.255.255.255
Binary : 1000 0000.0000 0000.0000 0000.0000 0000 - 1011 1111.1111 1111.1111 1111.1111 1111
And for class B the first two bits stay 10
Class C
Decimal : 192.0.0.0 - 223.255.255.255
Binary : 1100 0000.0000 0000.0000 0000.0000 0000 - 1101 1111.1111 1111.1111 1111.1111 1111
And for class C the first three bits stay 110
Class D
Decimal : 224.0.0.0 - 239.255.255.255
Binary : 1110 0000.0000 0000.0000 0000.0000 0000 - 1110 1111.1111 1111.1111 1111.1111 1111
And for class D the first four bits stay 1110
Class E
Decimal : 240.0.0.0 - 255.255.255.255
Binary : 1111 0000.0000 0000.0000 0000.0000 0000 - 1111 1111.1111 1111.1111 1111.1111 1111
And for class E the first four bits stay 1111
This is all moving away slowly though, IPv6 is bringing exciting changes as integrated IPsec, QoS and more.
Sami Guirguis
