3com 3031 Instruccion De Instalación

C

HAPTER

 30: DHCP C

ONFIGURATION

A DHCP server selects an IP address for a client in the following order: 

The static IP address bound to the MAC address of the client in the database of 
the DHCP server. 

The client’s previous IP address, i.e., the address requested in the “Requested IP 
Addr Option” carried in the DHCP_Discover packet sent by the client. 

A new address allocated from the server's DHCP pool of available addresses. This 
address is the one found first in the address pool. 

If the DHCP server does not find an available address, it will look outdated leased 
IP address and then ever conflicting IP address to find a valid one for assignment. If 
the attempt fails, the server will report error.

DHCP Server 

DHCP servers are well-suited to the network where: 

■

The network size is large, manual configuration is not an easy job, and it is hard 
to centralize the management on the entire network. 

■

The number of IP addresses available to the hosts on the network is far from 
adequate and it is impossible to assign a fixed IP address to each host. So the 
hosts, being too many, have to obtain dynamic IP addresses from a DHCP 
server in this case. In addition, limitation is placed on the number of concurrent 
users.

On networks, most hosts are not assigned fixed IP addresses except of a few of 
them. 

As shown in the following figure, a typical DHCP application network usually 
comprises a DHCP server and multiple clients (such as PCs and laptop computers). 

Figure 101   Typical networking for a DHCP server application

LAN

DHCP Server

DHCP Client

DHCP Client

DHCP Client

DHCP Client