H3C Technologies H3C S12500 Series Switches - Manual (Page 30)

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Configuring IP addressing
The IP addresses in this chapter refer to IPv4 addresses unless otherwise specified.
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Overview
This section describes the IP addressing basics.
IP addressing uses a 32-bit address to identify each host on an IPv4 network. To make addresses easier
to read, they are written in dotted decimal notation, each address being four octets in length. For
example, address 00001010000000010000000100000001 in binary is written as 10.1.1.1.
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IP address classes
Each IP address breaks down into the following sections:
• Net ID—Identifies a network. The first several bits of a net ID, known as the class field or class bits,
identify the class of the IP address.
• Host ID—Identifies a host on a network.
IP addresses are divided into five classes, as shown in
662H
Figure 6 . The shaded areas represent the address
class. The first three classes are most commonly used.
Figure 6 IP address classes
Table 1 IP address classes and ranges
Class Address range Remarks
A 0.0.0.0 to 127.255.255.255
The IP address 0.0.0.0 is used by a host at startup for
temporary communication. This address is never a valid
destination address.
Addresses starting with 127 are reserved for loopback
test. Packets destined to these addresses are processed
locally as input packets rather than sent to the link.
B 128.0.0.0 to 191.255.255.255 N/A
C 192.0.0.0 to 223.255.255.255 N/A
D 224.0.0.0 to 239.255.255.255 Multicast addresses.