Addresses

Address Classes

Traditional address classes
Address Class Characteristics
Class Length of network
address (octets)
First number Number of
local addresses
A10-12716,277,216
B2128-19165,536
C3192-223256

Addresses Not Connected to the Internet

Several blocks of addresses have been reserved for use for networks that will not be connected to the Internet and will never require connectivity to another organization. These addresses include:

	10.0.0.0 - 10.255.255.255
	172.16.0.0 - 172.31.255.255
	192.168.0.0 - 192.168.255.255

Note that many organizations will be using these addresses.

Inefficiency Caused By Address Classes

A Class A network spans 16,277,216 addresses, while Class B supports 65,536 and Class C only includes 256 numbers. The large gaps between these numbers led to very inefficient address block allocations and contributed to the depletion of the IP address space.

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