For those who need a reference, here is the excel spreadsheet.

2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0 bit

128 64 32 16 8 4 2 1 value

2 4 8 16 32 64 128 0 number of networks

Subnet Examples: Class C only

The /24 is called CIDR notation CIDR means Classless inter-domain routing notation

subnet /24

192 168 1 0 Network ID

255 255 255 0 Subnet

Available hosts: Formula is 2^n - 2

if subnet is /24, then the number of hosts is 254

subnet addr is 255.255.255.0

if subnet is /25, then the number of hosts is 126

subnet addr is 255.255.255.128 total number of available addresses on a /24 network is 256

using formula that becomes 254

total number of available addresses on a /25 network is 128

using formula that becomes 126

Network ID addr is 192.168.1.0

Network 1 : Network ID

addr is 192.168.1.0

First addr to use is 192.168.1.1

First addr to use is 192.168.1.1

Last addr to use is 192.168.1.254

Last addr to use is 192.168.1.126

Broadcast addr is 192.168.1.255

Broadcast addr is 192.168.1.127

Network 2: Network ID addr is 192.168.1.128

First addr to use is 192.168.1.129

Last addr to use is 192.168.1.254

Broadcast addr is 192.168.1.255

Official definition : Classless Inter-Domain Routing (CIDR) is an IP address allocation method that improves data routing efficiency on the internet. Every machine, server, and end-user device that connects to the internet has a unique number, called an IP address, associated with it.

Note: you can use this method with other IP classes (A and B). This only includes the non routable IP addresses in a network.

The range of the non routable ip addr is as follows

A: 10.0.0.0 - 10.255.255.255 (CIDR = 10.0.0.0/8)

B: 172.16.0.0 - 172.31.255.255 (CIDR = 172.16.0.0/16)

C: 192.168.0.0 - 192.168.255.255 (CIDR = 192.168.0.0/24)