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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)

DHCP Lease Address Pools, Ranges (Scopes) and Address Management 1 DHCP Overview of Client and Server Responsibilities

The “big news” in DHCP is dynamic address allocation, and the concept of address leasing. It is in fact this new functionality that makes DHCP significantly more complex than its predecessor. BOOTP is a simple request/reply protocol because a server only needs to look up a client's hardware address and send back the client's assigned IP address and other parameters. In contrast, DHCP clients and servers must do much more to carry out both parameter exchange and the many tasks needed to manage IP address leasing.

In this section I delve into the “nuts and bolts” of how DHCP operates. I begin with two background topics. The first provides an overview of the responsibilities of clients and servers in DHCP, and shows in general terms how they relate to each other. The second discusses DHCP configuration parameters and how they are stored and communicated.

The remaining five topics illustrate the operation of DHCP in detail. The first of the five describes the DHCP client finite state machine, which will give you a high-level look at the entire client lease “life cycle”, including address allocation, reallocation, renewal, rebinding and optionally, lease termination. This theoretical description is then used as the basis for several topics that explain the actual processes by which DHCP client lease activities occur. These show the specific actions taken by both client and server and when and how DHCP messages are created and sent. The last of the five topic describes the special mechanism by which a device not using DHCP for address allocation can request configuration parameters.

DHCP Lease Address Pools, Ranges (Scopes) and Address Management 1 DHCP Overview of Client and Server Responsibilities