56 DHCP OVERVIEWIntroduction to DHCP With networks getting larger in size and more complicated in structure, lack ofavailable IP addresses becomes the common situation the network administratorshave to face, and network configuration becomes a tough task for the networkadministrators. With the emerging of wireless networks and the using of laptops,the position change of hosts and frequent change of IP addresses also require newtechnology. Dynamic host configuration protocol (DHCP) is developed in thisbackground.DHCP adopts a client/server model, where DHCP clients send requests to DHCPservers for configuration parameters; and the DHCP servers return thecorresponding configuration information such as IP addresses to configure IPaddresses dynamically.A typical DHCP application includes one DHCP server and multiple clients (such asPCs and laptops), as shown in Figure 152.Figure 152 Typical DHCP applicationDHCP IP AddressAssignmentIP Address AssignmentPolicyCurrently, DHCP provides the following three IP address assignment policies tomeet the requirements of different clients:■ Manual assignment. The administrator statically binds IP addresses to fewclients with special uses (such as WWW server). Then the DHCP server assignsthese fixed IP addresses to the clients.■ Automatic assignment. The DHCP server assigns IP addresses to DHCP clients.The IP addresses will be occupied by the DHCP clients permanently.DHCP client DHCP clientDHCP client DHCP clientDHCP server
