Classless Inter-Domain Routing also known as the CIDR
notation is an alternate mode of representing a subnet mask. It is a count of
the number of network bits set to 1 in the subnet mask. It is preceded by a
hash sign “/”. To answer your question, the subnet 255.255.255.0 would be
represented as /24 and in binary would be written as 11111111 11111111 11111111
00000000
