Asus GigaX2124 - Manual (Page 109)

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Chapter 6 - IP Addresses, Network Masks, & Subnets
ASUS GigaX2124
Table 8: IP address structure
Field1 Field2 Field3 Field4
Class A Network ID Host ID
Class B Network ID Host ID
Class C Network ID Host ID
Here are some examples of valid IP addresses:
Class A: 10.30.6.125 (network = 10, host = 30.6.125)
Class B: 129.88.16.49 (network = 129.88, host = 16.49)
Class C: 192.60.201.11 (network = 192.60.201, host = 11)
6.1.2 Network classes
Classes A, B, and C are the three commonly used network classes.
(There is also a class D but it has a special use beyond the scope of this
discussion.) These classes have different uses and characteristics.
Class A networks are the Internet’s largest networks, each with room for
over 16 million hosts. Up to 126 of these huge networks can exist, for a
total of over 2 billion hosts. Because of their huge size, these networks
are used for WANs and by organizations at the infrastructure level of the
Internet, e.g. your ISP.
Class B networks are smaller but still quite large, each being able to
hold over 65,000 hosts. There can be up to 16,384 class B networks in
existence. A class B network might be appropriate for a large organization
such as a business or government agency.
Class C networks are the smallest, only able to hold 254 hosts at most, but
the total possible number of class C networks exceeds 2 million (2,097,152
to be exact). LANs connected to the Internet are usually class C networks.
The class can be determined easily from field1:
field1 = 1-126: Class A
field1 = 128-191: Class B
field1 = 192-223: Class C
(field1 values not shown are reserved for special uses)
A host ID can have any value except all fields set to 0 or all fields set to
255, as those values are reserved for special uses.