Инструкции По Установке для 3com S7906E

 

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DHCP supports three mechanisms for IP address allocation. 

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Manual allocation: The network administrator assigns an IP address to a client like a WWW server, 

and DHCP conveys the assigned address to the client. 

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Automatic allocation: DHCP assigns a permanent IP address to a client. 

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Dynamic allocation: DHCP assigns an IP address to a client for a limited period of time, which is 

called a lease. Most DHCP clients obtain their addresses in this way. 

Figure 1-2 Dynamic IP address allocation process 

 

 

As shown in 

, a DHCP client obtains an IP address from a DHCP server via four steps: 

2)  The client broadcasts a DHCP-DISCOVER message to locate a DHCP server. 

3)  A DHCP server offers configuration parameters including an IP address to the client in a 

DHCP-OFFER message. The sending mode of the DHCP-OFFER message is determined by the 

flag field in the DHCP-DISCOVER message. Refer to 

 for related 

information. 

4)  If several DHCP servers send offers to the client, the client accepts the first received offer, and 

broadcasts it in a DHCP-REQUEST message to formally request the IP address. 

5)  All DHCP servers receive the DHCP-REQUEST message, but only the server from which the client 

accepts the offered IP address responds. The server returns a DHCP-ACK message to the client, 

confirming that the IP address has been allocated to the client, or a DHCP-NAK unicast message, 

denying the IP address allocation.