Here's a table showing the relationship between the / notation, the byte
notation, and the corresponding binary numbers (with a dot every eight
digits) for the 32 bit addresses. I've thrown in a count of how many
Class A/B/C networks the larger networks encompass.
/ Notation Binary Byte Notation #Class
---------- ----------------------------------- -------------- ------
/0 00000000.00000000.00000000.00000000 0.0.0.0 256 A
/1 10000000.00000000.00000000.00000000 128.0.0.0 128 A
/2 11000000.00000000.00000000.00000000 192.0.0.0 64 A
/3 11100000.00000000.00000000.00000000 224.0.0.0 32 A
/4 11110000.00000000.00000000.00000000 240.0.0.0 16 A
/5 11111000.00000000.00000000.00000000 248.0.0.0 8 A
/6 11111100.00000000.00000000.00000000 252.0.0.0 4 A
/7 11111110.00000000.00000000.00000000 254.0.0.0 2 A
/8 11111111.00000000.00000000.00000000 255.0.0.0 1 A
/9 11111111.10000000.00000000.00000000 255.128.0.0 128 B
/10 11111111.11000000.00000000.00000000 255.192.0.0 64 B
/11 11111111.11100000.00000000.00000000 255.224.0.0 32 B
/12 11111111.11110000.00000000.00000000 255.240.0.0 16 B
/13 11111111.11111000.00000000.00000000 255.248.0.0 8 B
/14 11111111.11111100.00000000.00000000 255.252.0.0 4 B
/15 11111111.11111110.00000000.00000000 255.254.0.0 2 B
/16 11111111.11111111.00000000.00000000 255.255.0.0 1 B
/17 11111111.11111111.10000000.00000000 255.255.128.0 128 C
/18 11111111.11111111.11000000.00000000 255.255.192.0 64 C
/19 11111111.11111111.11100000.00000000 255.255.224.0 32 C
/20 11111111.11111111.11110000.00000000 255.255.240.0 16 C
/21 11111111.11111111.11111000.00000000 255.255.248.0 8 C
/22 11111111.11111111.11111100.00000000 255.255.252.0 4 C
/23 11111111.11111111.11111110.00000000 255.255.254.0 2 C
/24 11111111.11111111.11111111.00000000 255.255.255.0 1 C
/25 11111111.11111111.11111111.10000000 255.255.255.128
/26 11111111.11111111.11111111.11000000 255.255.255.192
/27 11111111.11111111.11111111.11100000 255.255.255.224
/28 11111111.11111111.11111111.11110000 255.255.255.240
/29 11111111.11111111.11111111.11111000 255.255.255.248
/30 11111111.11111111.11111111.11111100 255.255.255.252
/31 11111111.11111111.11111111.11111110 255.255.255.254
/32 11111111.11111111.11111111.11111111 255.255.255.255
Here's an example of how to get from the binary number 11000000 to
the decimal number (192).
11000000 => 128*1 + 64*1 + 32*0 + 16*0 + 8*0 + 4*0 + 2*0 + 1*0
= 128 + 64 + 0 + 0 + 0 + 0 + 0 + 0
= 128 + 64
= 192
Another example (using an arbitrarily chosen binary number):
10000100 => 128*1 + 64*0 + 32*0 + 16*0 + 8*0 + 4*1 + 2*0 + 1*0
= 128 + 0 + 0 + 0 + 0 + 4 + 0 + 0
= 128 + 4
= 132
