Subnetting identifies a network with a range of Internet Protocol addresses in the Internet. It also allows large networks to be divided into smaller networks, each with its own set of IP addresses.
The subnet mask is the value assigned during subnetting. If, for example, your Internet Service Provider has given you an IP address of 192.168.0.1/24, it means that your subnet mask is 255.255.255.0. The 24 value represents the 24 1's of the binary equivalent of 255.255.255.0, which is 11111111.11111111.11111111.0 A /32 subnet mask means that there are 32 1's from left to right and is equivalent to 255.255.255.255.
Subnetting identifies how many computers with unique IP addresses can be available in the network. This is determined, again, by its subnet mask. The number of computers is determined by subtracting the last value in the subnet mask from 256. A 255.255.255.0 subnet mask has a last value of 0, thus there are 256 maximum computers available. A 255.255.255.240 can host a maximum of 16 computers.
The first and the last IP addresses in a subnet are reserved. In reality, a /24 subnet can host a maximum number of 254 computers. The maximum count is always minus 2 because the first IP address is considered as the network ID, which is how a network is identified in the Internet. The last IP address is the broadcast ID, which is used by computers inside the network to forward or broadcast data.