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 Allocation Mechanisms 1 2 3 4 DHCP Lease "Life Cycle" Overview (Allocation, Reallocation, Renewal, Rebinding and Release) and Lease Timers

Of the three address allocation methods supported by DHCP, dynamic address allocation is by far the most popular and important. The significance of the change that dynamic addressing represents to how IP addresses are used in TCP/IP can be seen in the semantics of how addresses are treated in DHCP. Where conventionally a host was said to own an IP address, when dynamic address allocation is used, hosts are said instead to lease an address.

The notion of a “lease” conveys very accurately the difference between dynamic allocation and the other types. A host no longer is strictly “entitled” to a particular address, with a server merely telling it what the address is. In DHCP, the server remains the real owner of all the IP addresses in the address pool, and merely gives permission for a client to use the address for a period of time. The server guarantees that it will not try to use the address for another client only during this time. The client is responsible for taking certain actions, as we will see later in this section, if it wants to continue using the address. If it does not successfully reacquire permission for using the address after a period of time, it must stop using it, or risk creating an IP address conflict on the network.

DHCP Address Assignment and Allocation Mechanisms 1 2 3 4 DHCP Lease "Life Cycle" Overview (Allocation, Reallocation, Renewal, Rebinding and Release) and Lease Timers