Network Classes; Table 13.1 Ip Address Structure - Asus iPBX30 User Manual

iPBX30 User Manual
Field 1
Class A
Network ID
Class B
Class C
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)
13.2

Network classes

The three commonly used network classes are A, B, and C. (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, such as your ISP.
Class B networks are smaller but still quite large, each 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.
Some important notes regarding IP addresses:
The class can be determined easily from field1:
field1 = 1-126:
field1 = 128-191:
field1 = 192-223:
(field1 values not shown are reserved for special uses)
Table 13.1. IP Address Structure
Field 2
Network ID
Network ID
Class A
Class B
Class C
Field 3 Field 4
Host ID
Host ID
Host ID
Chapter 13
135