Figure 1-1. Three Main Address Classes - NETGEAR RT338 Reference Manual

Reference Guide for the Model RT338 ISDN Router
There are five standard classes of IP addresses. The address classes determine the network and
host sections of the address differently. Address classes allow for different numbers of hosts on a
network. Each address type begins with a unique bit pattern, which is used by the TCP/IP software
to identify the address class. After the address class has been determined, the software can
correctly identify the host section of the address. The three main address classes are illustrated in
Figure 1-1, which shows the network and node sections of the address for each address type.
Class A
Network
Class B
Network
Class C
Network
Figure 1-1. Three Main Address Classes
IP address classes are described in
Table 1-1. Address Classes
Address
Range
Class
A 1.x.x.x to 126.x.x.x Class A addresses can have up to 16,777,214 hosts on a single network.
B 128.1.x.x to
191.254.x.x
C 192.0.1.x to
223.255.254.x
D 224.0.0.0 to
239.255.255.255
E
1-8
Node
Node
Node
Table 1-1.
Description
They use an 8-bit network number and a 24-bit node number.
Class B addresses can have up to 65,354 hosts on a network. They use a
16-bit network number and a 16-bit node number.
Class C addresses can have 254 hosts on a network. They use 24 bits for
the network address and 8 bits for the node.
Class D addresses are used for multicasts (messages sent to many hosts).
Class E addresses are for experimental use.
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Introduction