The subnet mask is used to divide a network into a further sub network within A private network. Subnetting can be used for security purpose in many cases it enable a network administrator to divide a college network for example into many departments like Botany, Art and Science group network.
Subnetting is applied on host id we reserve host id bits for subnetting from left to right following example depict all aspects of operation
What is Subnetting?
Subnetting enables the network administrator to further divide the host part of the address into two or more subnets. In this case, a part of the host address is reserved to identify the particular subnet. This is easier to see if we show the IP address in binary format.The full address is: