3com 3.01.01 User Manual

C

HAPTER

 4: N

ETWORK

 P

ROTOCOL

 O

PERATION

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IP protocol allocates one IP address for each network interface. Multiple IP 
addresses can only be allocated to a device which has multiple network interfaces. 
IP addresses on a device with multiple interfaces have no relationship among 
themselves. 

With the rapid development of the Internet, IP addresses are depleting very fast. 
The traditional IP address allocation method uses up IP addresses with little 
efficiency. The concept of mask and subnet was proposed to make full use of the 
available IP addresses.

A mask is a 32-bit number corresponding to an IP address. The number consists of 
1s and 0s. Principally, these 1s and 0s can be combined randomly. However, the 
first consecutive bits are set to 1s when designing the mask. The mask is divided 
into two parts, the subnet address and host address. The 1 bits and the mask 
indicate the subnet address, and the other bits indicate the host address. 

If there is no sub-net division, then the sub-net mask is the default value and the 
length of “1” indicates the net-id length. Therefore, for IP addresses of classes A, 
B and C, the default values of the corresponding sub-net mask is 255.0.0.0 for 
Class A, 255.255.0.0 for Class B, and 255.255.255.0 for Class C.

The mask can be used to divide a Class A network containing more than 
16,000,000 hosts or a Class B network containing more than 60,000 hosts into 
multiple small networks. Each small network is called a subnet. For example, for 
the Class A network address 10.110.0.0, the mask 255.255.224.0 can be used to 
divide the network into 8 subnets: (10.110.0.0, 10.110.32.0, 10.110.64.0, and so 
on). Each subnet can contain more than 8000 hosts. 

The following sections describe the tasks for configuring an IP address:

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This command creates correspondence between the name and the IP address of 
the host. When you use applications like Telnet, you can use the host name 
without having to memorize the IP address because the system translates the 
name to the IP address automatically.

Perform the following configuration in System view.

By default, there is no host name associated to any host IP address.

Table 1   Configure the Host Name and the Corresponding IP Address

Configure the host name and the 
corresponding IP address

ip host hostname ip-address

Delete the host name and the corresponding 
IP address

undo ip host hostname [ ip-address ]