Classless Internet Domain Routing (CIDR)
Class A addresses are long gone, and the world is quickly running out of Class B addresses. Class C addresses are still available, but the small address space of a Class C network (254 hosts maximum) is a severe limitation in the high-volume game of Internet service providers (ISPs). It is possible to assign a range of Class C networks to a network owner who needs more than 254 addresses. However, treating multiple Class C networks as separate entities when they are all going to the same place only clutters up routing tables unnecessarily.
As you learned earlier in this hour, the address class system is relatively inflexible and requires a subnetting system for more granular control of the address space. ...
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