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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)            9  Host Configuration and TCP/IP Host Configuration Protocols (BOOTP and DHCP)                 9  TCP/IP Dynamic Host Configuration Protocol (DHCP)                      9  DHCP Address Assignment and Dynamic Address Allocation and Management

DHCP Address Assignment and Dynamic Address Allocation and Management 1 2 3 4 DHCP Leases, Lease Length Policies and Management

Manual Allocation

Manual allocation is the simplest method, and is equivalent to the method BOOTP uses for address assignment. Each device has an address that an administrator gives it ahead of time, and all DHCP does is look up the address in a table and send it to the client for which it is intended. This technique makes the most sense for devices that are “mainstays” of the network, such as servers and routers. It is also appropriate for other devices that for whatever reason must have a stable, permanent IP address.

Okay, now here's a fair question you might have. DHCP acts basically like BOOTP in the case of manual allocation. But BOOTP was created for devices that needed help with configuration. Servers and routers are complex devices with their own internal storage, and obviously don't need a DHCP server to tell them their IP address like a diskless workstation does, so why bother using DHCP for them at all?

Well, in fact, you could just manually assign the address to the device directly and tell DHCP to ignore those addresses. However, using DHCP for manual assignments yields a different benefit: an administrative one. It keeps all the IP address information centralized in the DHCP address database, instead of requiring an administrator to go from machine to machine checking addresses and ensuring there are no duplicates. Updates can also be made in a single place as well.

DHCP Address Assignment and Dynamic Address Allocation and Management 1 2 3 4 DHCP Leases, Lease Length Policies and Management