Figure 1-1. Three Main Address Classes - NETGEAR RH348 Reference Manual

Reference Guide for the Model RT328 and Model RH348 ISDN Routers
There are five standard classes of IP addresses. These address classes have different ways of
determining the network and host sections of the address, allowing 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 host sections of the address for each address type.
Class A
Network
Class B
Network
Class C
Network
Figure 1-1. Three Main Address Classes
Class A addresses can have up to 16,777,214 hosts on a single network. They use an 8-bit network
number and a 24-bit node number. Class A addresses are in this range:
1.x.x.x to 126.x.x.x.
Class B addresses can have up to 65,354 hosts on a network. A Class B address uses a 16-bit
network number and a 16-bit node number. Class B addresses are in this range:
128.1.x.x to 191.254.x.x.
Class C addresses can have 254 hosts on a network. Class C addresses use 24 bits for the network
address and 8 bits for the node. They are in this range:
192.0.1.x to 223.255.254.x.
Class D addresses are used for multicasts (messages sent to many hosts). Class D addresses are in
this range:
224.0.0.0 to 239.255.255.255.
1-8
Node
Node
Node
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Introduction