IP Supernetting: CIDR Hierarchical Addressing and Notation
When you first looked at IP addressing in Chapter 17, you saw that IP addresses were designed to be divided into a network identifier (network ID) and host identifier (host ID). Then, when subnets were introduced, you "stole" bits from the host ID to create a subnet ID, giving the IP address a total of three hierarchical levels. With VLSM, you further subnetted the subnets, taking more bits from the host ID to give you a multiple-level hierarchy with sub-subnets, sub-sub-subnets, and so forth.
In a classless environment, you completely change how you look at IP addresses by applying VLSM concepts not just to one network, but to the entire Internet. In essence, the Internet becomes just ...
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