Saturday, February 15, 2014

IPv4 Address Classes

Though Classless Inter-Domain Routing (CIDR) and Variable-Length Subnet Mask (VLSM) are the order of today's IPv4 networking, classification of IPv4 address spaces into classes A, B, C, or D remains common. The following table shows the classes that were designated during the days of classful routing:

Class First bits Address range Subnet mask
Class A 0 1.x.x.x ~ 127.x.x.x (/8)
Class B 10 128.0.x.x ~ 191.255.x.x (/16)
Class C 110 192.0.0.x ~ 223.255.255.x (/24)
Class D 1110 ~ -
Class E 1111 ~ -

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