Sometimes a certain number of subnets is required, with less emphasis on the number of host addresses per subnet. This may be the case if an organization chooses to separate their network traffic based on internal structure or department setup. For example, an organization may choose to put all host devices used by employees in the Engineering department in one network, and all host devices used by management in a separate network. In this case, the number of subnets is most important in determining how many bits to borrow.

Recall the number of subnets created when bits are borrowed can be calculated using the formula 2^n (where n is the number of bits borrowed). There is no need to subtract any of the resulting subnets, as they are all usable.

The key is to balance the number of subnets needed and the number of hosts required for the largest subnet. The more bits borrowed to create additional subnets means fewer hosts available per subnet.