IP Addresses 85
referred to as a field or an octet. Decimal notation converts the value of 
each field into a decimal number, and the fields are separated by dots.
Figure 25   Dotted Decimal Notation for IP Addresses
The decimal value of an octet whose bits are all 1s is 255.
Network Portion
The location of the boundary between the network part and the host 
part depends on the class that the central agency assigns to your 
network. The three primary classes of IP addresses are as follows:
■ Class A address — Uses 8 bits for the network part and 24 bits for 
the host part. Although only a few Class A networks can be created, 
each can contain a very large number of hosts.
■ Class B address — Uses 16 bits for the network part and 16 bits for 
the host part. 
■ Class C address — Uses 24 bits for the network part and 8 bits for 
the host part. Each Class C network can contain only 254 hosts, but 
many such networks can be created.
The high-order bits of the network part of the address designate the IP 
network class. See Table 11
.
Table 11   How Address Class Corresponds to the Address Number
Address Class High-order Bits
Address Number 
(Decimal)
A 0nnnnnnn 0-127
B 10nnnnnn 128-191
C 11nnnnnn 192-254
158.101.10.32
10011110.01100101.00001010.00100000 = Binary notation
= Decimal notation