∙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.
∙Automatic allocation: DHCP assigns a permanent IP address to a client.
∙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.
Dynamic IP address allocation process
a.Dynamic IP address allocation process
As shown in a, a DHCP client obtains an IP address from a DHCP server via four steps: Table 77 The client broadcasts a
Table 78 A DHCP server offers configuration parameters such as an IP address to the client in a
Table 79 If several DHCP servers send offers to the client, the client accepts the first received offer, and broadcasts it in a
Table 80 All DHCP servers receive the
NOTE:
After the client receives the
IP addresses offered by other DHCP servers are still assignable to other clients.
IP address lease extension
The IP address dynamically allocated by a DHCP server to a client has a lease. When the lease expires, the DHCP server will reclaim the IP address. If the client wants to use the IP address longer, it has to extend the lease duration.
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