3com 8807 User Guide

IP A

DDRESS

ONFIGURATION

Introduction to IP
Addresses

IP Address Classification

and Representation

An IP address is a 32-bit address allocated to a device that accesses the Internet. It
consists of two fields: net-id field and host-id field. IP addresses are allocated by
Network Information Center (NIC) of American Defense Data Network (DDN). To
manage IP addresses conveniently, IP addresses are classified into five types. See
the following figure.

Figure 14 Five classes of IP addresses

Here, Class A, Class B and Class C addresses are unicast addresses, while Class D
addresses are multicast ones and class E addresses are reserved for special
applications in future. The first three types are commonly used.

The IP address is in dotted decimal format. Each IP address contains four integers
in dotted decimal notation. Each integer corresponds to one byte, for example,
10.110.50.101.

When using IP addresses, note that some of them are reserved for special uses,
and are seldom used. The IP addresses you can use are listed in the following
table.

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

1 0

1 1 0

1 1 1 0

1 1 1 1 0

net-id

Multicast address

Reserv ed

host-id

Class A

Class B

Class C

Class D

Class E

net-id: network ID host-id: Host ID