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)

DHCP Overview, Motivation, History and Standards 1 DHCP Address Assignment and Allocation Mechanisms

The Dynamic Host Configuration Protocol (DHCP) was created as an extension of the older Boot Protocol (BOOTP). The first word in “DHCP” describes the most important new capability that was added to BOOTP: the ability to assign IP addresses dynamically. Moving from a static to a dynamic address allocation model dramatically changes the way we deal with IP addresses in DHCP. Host configuration is transformed from a simple way to tell a host what its address and other parameters are, to a complete tool for managing IP addresses in an organization.

In this section I begin my detailed look at DHCP by describing the concepts behind DHCP address assignment and leases. I begin with a look at how DCHP address assignment works, and a description of the three DHCP address allocation mechanisms. I then delve into DHCP leases and the policies and techniques used to decide how to implement DHCP leasing. I provide an overview of the lease “life cycle” from start to finish, and describe the two DHCP lease timers that help control the process. Finally, I describe DHCP lease address pools and ranges and the general concepts behind address management.

DHCP Overview, Motivation, History and Standards 1 DHCP Address Assignment and Allocation Mechanisms