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Computer Network 2021
The assumption was that there would be a relatively small number of large networks,
possibly with millions of computers.
The designers envisioned a larger number of medium-sized networks, with perhaps
thousands of computers each.
Finally, they saw a great number of networks having several hundred or fewer machines.
Thus, the designers divided the available IP addresses into classes to define the large
(Class A), medium (Class B), and small (Class C) networks, as shown in Table 4-2.
Knowing the class of an IP address is the first step in determining which part of the
address identifies the network and which part identifies the host.
Table 4-2 shown an Identifying Address Classes
4.2.3 IP Address Classes
To accommodate different-sized networks and to aid in classifying them, IP addresses
are divided into groupings called classes, as shown in Figure 4-10. This is called classful
addressing. Each complete 32-bit IP address is broken into a network part and a host part. A bit
or bit sequence at the start of each address determines the class of the address, as shown in
Figure 4-11.
There are five IP address classes.
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