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TCP/IP 41
Table 3.1: Features of the different classes
Class A Net ID byte 1, first bit is always 0, (0 x x x x x x x)
126 possible network addresses
Host ID byte 2 + byte 3 + byte 4
16777214 possible hosts per network
Range
1 . n . n . n → 126 . n . n . n
Example 90.15.167.2 (network name 90.0.0.0)
Class B Net ID byte 1, first bits are always 1 0, (1 0 x x x x x x) + byte 2
16383 possible network addresses
Host ID byte 3 + byte 4
65534 possible hosts per network
Range
128 . 0 . n . n → 191 . 255 . n . n
Example 128.19.205.132 (network name 128.19.0.0)
Class C Net ID byte 1, first bits are always 1 1 0, (1 1 0 x x x x x) + byte 2 + byte 3
2097152 possible network addresses
Host ID byte 4
254 possible hosts per network
Range
192 . 0 . 0 . n → 223 . 255 . 255 . n
Example 192.147.25.112 (network name 192.147.25.0)
The use of IP addresses is controlled by the Internet Assigned Number Authority (IANA).
IP addresses for private networks
Distinction is drawn between public networks and private networks (corporate networks). On
the Internet (the whole of public networks), every IP address has to be unique. Corporate
networks are linked to the Internet via a router. In order to avoid conflicts between private
networks and public networks, a series of IP addresses that are not used on the Internet are
defined within each class. These are described in RFC 1597, Reserved Address Space. A
corporate network preferably uses a value from this series as name, see Table 3.2 .