A subnet allows the flow of network traffic between hosts to be segregated based on a network configuration. By organizing hosts into logical groups, sub netting can improve network security and performance. Because here the routing tables become much shorter by using the subnet addresses and this means that the data flow also becomes faster. In the same time it enables the network administrator to further divide the host part of the address into two or more subnets. So the network administrators can assign IP numbers to specific departments.
So they can easily identify the departments on the network using the same numbers. Not only that it specific department can now handle all the computers in their own network without depending on the network administrator. In the same time it removes physical barriers and since the networks now are individually identified all the networks can be connected through routers. Also it reduce number of routes needed. Because only need to know the one common network address for all the individual computers and devices on the different subnets. While concerning all these things we can say that sub netting is really important