CIDR Notation
CIDR stands for Classless Inter-Domain Routing. CIDR was developed in the 1990s as a standard scheme for routing network traffic across the Internet.
/27 1/8th of a Class C 32 hosts
/26 1/4th of a Class C 64 hosts
/25 1/2 of a Class C 128 hosts
/24 1 Class C 256 hosts
/23 2 Class C 512 hosts
/22 4 Class C 1,024 hosts
/21 8 Class C 2,048 hosts
/20 16 Class C 4,096 hosts
/19 32 Class C 8,192 hosts
/18 64 Class C 16,384 hosts
/17 128 Class C 32,768 hosts
/16 256 Class C 65,536 hosts (= 1 Class B)
/15 512 Class C 131,072 hosts
/14 1,024 Class C 262,144 hosts
/13 2,048 Class C 524,288 hosts
(more…)