Other Classes

In addition to the three most popular classes, there are two additional

classes. Class D addresses have their leading four bits set to 1 1 1 0 and

are used to support IP Multicasting. Class E addresses have their leading

four bits set to 1 1 1 1 and are reserved for experimental use. 

Dotted Decimal Notation

To make Internet addresses easier for people to read and write, IP

addresses are often expressed as four decimal numbers, each separated

by a dot. This format is called  dotted decimal notation.  

Dotted decimal notation divides the 32 bit Internet address into four 8 

bit fields and specifies the value of each field independently as a deci 

mal number with the fields separated by dots. Figure 5 shows how a

typical /16 (Class B) Internet address can be expressed in dotted decimal

notation. 

F I G U R E   5 .   D o t t e d   D e c i m a l   N o t a t i o n

Table 1 displays the range of dotted decimal values that can be assigned

to each of the three principle address classes. The  xxx  represents the

host number field of the address that is assigned by the local network

administrator. 

TA B L E   1 .   D o t t e d   D e c i m a l   R a n g e s   f o r   E a c h   A d d re s s   C l a s s

5