3com 3.01.01 用户手册

This chapter covers the following topics:

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IP address is a 32-bit address represented by four octets. IP addresses are divided 
into five classes, A, B, C, D and E. The octets are set according to the first few bits 
of the first octet. 

The rule for IP address classification is described as follows:

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Class A addresses are identified with the first bit of the first octet being 0.

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Class B addresses are identified with the first bits of the first octet being 10.

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Class C addresses are identified with the first bits of the first octet being 110.

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Class D addresses are identified with the first bits of the first octet being 1110.

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Class E addresses are identified with the first bits of the first octet being 11110.

Addresses of Classes A, B and C are unicast addresses. The Class D addresses are 
multicast addresses and Class E addresses are reserved for future uses.

At present, IP addresses are mostly Class A, Class B and Class C. IP addresses of 
Classes A, B and C are composed of two parts, network ID and host ID. Their 
network ID lengths are different. 

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Class A IP addresses use only the first octet to indicate the network ID. 

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Class B IP addresses use the first two octets to indicate the network ID. 

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Class C IP addresses use the first three octets to indicate the network ID. 

At most, there are: 28 =128 Class A addresses, 216=16384 Class B addresses and 
224=2,097,152 Class C addresses.

The IP address is in dotted decimal format. Each IP address contains 4 integers in 
dotted decimal notation. Each integer corresponds to one byte, 
e.g.,10.110.50.101.

Configuring an IP Address is described in the following sections:

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