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Table Of Contents  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)

Previous Topic/Section
BOOTP Relay Agents (Forwarding Agents)
Previous Page
Pages in Current Topic/Section
1
Next Page
DHCP Overview, Motivation, History and Standards
Next Topic/Section

TCP/IP Dynamic Host Configuration Protocol (DHCP)

In some ways, technological advancement can be considered more a journey than a destination. When a particular technology is refined or replaced with a superior one, it's usually only a matter of time before it too is replaced with something better. And so it was with the TCP/IP Boot Protocol. While BOOTP was far more capable than the protocol it replaced (RARP), after a number of years BOOTP itself was replaced with a new TCP/IP configuration protocol: the Dynamic Host Configuration Protocol (DHCP).

Where BOOTP represented a revolutionary change from RARP, DHCP is more of an evolution of BOOTP. It was built using BOOTP as a foundation, with the same basic message format. The most significant addition in DHCP is the ability to dynamically assign addresses to clients and to centrally manage them. It is this capability that both gives DHCP its name, and makes it so powerful. DHCP today is the standard TCP/IP host configuration protocol and is used in everything from single-client home networks to enterprise-class internetworks.

In this section I describe the concepts behind DHCP and explain how it works in detail. I begin with a topic that provides an overview of the protocol, discussing its history and the standards that define it. I then have four subsections that describe DHCP concepts and operation. The first talks about the different ways DHCP can assign addresses, with a focus on dynamic addressing. The second discusses how DHCP operates, including a look at configuration parameter management and the procedures for allocating addresses and managing those allocations. The third describes DHCP messaging and illustrates the DHCP message format. The fourth gets into more of the details of DHCP clients and servers, and also looks at special features and issues with DHCP. Finally, I conclude with a topic describing how DHCP changes to support the new IP version 6.

Related Information: Since DHCP builds upon BOOTP, they have a number of things in common. For example, DHCP makes use of BOOTP relay agent functionality, and DHCP options are basically the same as BOOTP vendor information fields. Since DHCP is the more common of the two protocols, I have tried to be complete in describing the operation of these features here, highlighting especially any differences between how they work for DHCP compared to BOOTP.

However, I have avoided duplicating the history and reasoning for the existence of many of these features. Since BOOTP came first, I have placed more of the historical information in the BOOTP section. In general, if you plan to read about DHCP as well as BOOTP, I recommend reading
the section on BOOTP first. If you don't plan to read up on BOOTP, you may wish to check the topic on DHCP/BOOTP interoperability instead.


Quick navigation to subsections and regular topics in this section



Previous Topic/Section
BOOTP Relay Agents (Forwarding Agents)
Previous Page
Pages in Current Topic/Section
1
Next Page
DHCP Overview, Motivation, History and Standards
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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