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Ip Address Class

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Submitted By NotSo31
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IP Addresses Classes and Special-Use IP Address Space
History of IP Classes.
When IP was first standardized in September 1981, the specification required that each system attached to an IP-based Internet be assigned a unique, 32-bit Internet address value. Systems that have interfaces to more than one network require a unique IP address for each network interface. To provide the flexibility required to support networks of varying sizes, the Internet designers decided that the IP address space should be divided into three address classes-Class A, Class B, and Class C. This is often referred to as classful addressing. Each class fixes the boundary between the network prefix and the host number at a different point within the 32-bit address.
Class A
Class A network address has an 8-bit network prefix, with the highest order bit set to 0 (zero) and a 7-bit network number, followed by a 24-bit host number. Today, Class A networks are referred to as “/8s” since they have an 8-bit network prefix. A maximum of 126 (27 -2) /8 networks can be defined. Each /8 supports a maximum of 224 -2 (16,777,214) hosts per network. Since the /8 address block contains 231 (2,147,483,648) individual addresses and the IPv4 address space contains a maximum of 232 (4,294,967,296) addresses, the /8 address space is 50 percent of the total IPv4 unicast address space.
Class B
Class B network address has a 16-bit network prefix, with the two highest order bits set to 1-0 and a 14-bit network number, followed by a 16-bit host number. Class B networks are now referred to as “/16s” since they have a 16-bit network prefix. A maximum of 16,384 (214) /16 networks can be defined with up to 65,534 (216-2) hosts per network. Since the entire /16 address block contains 230 (1,073,741,824) addresses, it represents 25 percent of the total IPv4 unicast address space.

Class C
Class C network address

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