Subnet Masking
When network administrators create subnets, they borrow bits from the default host field to make a set of subnetworks.
The number of borrowed bits determines how many subnetworks and hosts will be available.
Whenever you subnet a network address, you lose some of the host addresses that you could have had without the subnetting.
As shown in the Table on the next slide, the network administrator can use up to 14 bits to subnet a Class B address.