3Com 3 manual Dotted Decimal Notation, Decimal value of an octet whose bits are all 1s is

IP Addresses 87

Dotted Decimal Notation

The actual IP address is a 32-bit number that is stored in binary format. These 32 bits are segmented into 4 groups of 8 bits — each group is 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 27 Dotted Decimal Notation for IP Addresses

10011110.01100101.00001010.00100000 = Binary notation

158.101.10.32 = Decimal notation

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 8.

Table 8 How Address Class Corresponds to the Address Number

		Address Number
Address Class	High-order Bits	(Decimal)
A	0nnnnnnn	0-127
B	10nnnnnn	128-191
C	11nnnnnn	192-254