Table of Contents
I. INTRODUCTION TO DHCP.
1. An Introduction to DHCP.
Configuring Devices on a Network. A First Attempt at Automating
Device Configuration. The Benefits of DHCP. Assigning IP Addresses
Using DHCP. Perceived Problems of DHCP. Address Allocation
Policies.
2. An Example of DHCP in Operation.
Setting Up the GSI Network. Using DHCP to Configure Computers.
Leases on IP Addresses in DHCP.
3. Configuring the DHCP
Server.
Specifying the Basic Network Architecture. Required Configuration
Parameters. Specifying Leases. Other DHCP Options. Extending a
Lease and Moving Between Subnets. Other Configuration
Information.
4. Configuring TCP/IP Stacks.
The TCP/IP Protocol Suite. The Physical Layer. The Data Link Layer.
The Internet Layer. The Transport Layer. The Application Layer.
II. DHCP THEORY OF OPERATION.
5. DHCP Client/Server Model.
DHCP Goals and Design Decisions. Related TCP/IP Protocols. The DHCP
Client/Server Architecture.
6. The Format of DHCP
Messages.
DHCP Message Format Overview. The Fixed-Format Section. The options
Section. Examples of Message Formats. Design Constraints.
7.
Transmitting DHCP Messages.
Using UDP for DHCP. Relay Agents. Reliable Delivery of DHCP
Messages. Other Transmission Methods. Authenticated DHCP
Messages.
8. DHCP Message Exchanges.
Client States. Working with Multiple Servers. Other Message
Exchanges.
9. DHCP Options.
DHCP-Specific Options. Host Configuration Parameters Options.
TCP/IP Stack Configuration Parameters. Service Parameter
Options.
10. Failover Protocol Operation.
Failover Protocol Overview. Lease Handling with Failover. Failover
Operational States. Binding Update Conflicts. Pool Rebalancing.
Complex Failover Configurations.
11. DHCP-DNS
Interaction.
The Domain Name System. DHCP and DNS. Dynamic Updates to the DNS
Database. Dynamic Updates and DHCP. How the DHCP Server Updates the
DNS.
III. DHCP SERVERS AND CLIENTS.
12. Theory of the Operation of a DHCP Server.
Address Allocation Strategy. Allocation and Renewal in Response to
a DHCPREQUEST Message. DHCP Message Handling. Abandoned Lease
Address Reclamation.
13. The Microsoft DHCP Server.
Installing the Microsoft DHCP Service. Managing DHCP Servers.
Configuring DHCP Servers. Controlling the Windows DHCP
Server.
14. The ISC DHCP Server.
Obtaining the ISC DHCP Server. Prerequisites to Operation of the
ISC DHCP Server. Configuring the ISC DHCP Server. Invoking the ISC
DHCP Server. Server Operation.
15. Configuring a DHCP
Server.
Configuring a DHCP Server to Be Authoritative. Configuring an
Individual Subnet. Supporting Multiple Network Segments.
Configuring Multiple IP Subnets on Each Network Segment.
16.
Client Identification and Fixed-Address Allocation.
Identifying Clients. Static Allocation. Mixing Static and Dynamic
Allocation. Automatic Allocation. Access Control.
17. Setting Up
a Reliable DHCP Service.
Determining Your Level of DHCP Service Reliability. Specific
Failures in DHCP Service. Improving Reliability by Using Long
Leases. Setting Up a Secondary DHCP Server. Problems with Setting
Up Redundant Servers.
18. Configuring a Failover Server.
Types of Failover Relationships. Setting Up Failover Service for
the First Time. Configuring the ISC DHCP Server to Do Failover.
Operating a Failover Pair. Issues Specific to the ISC DHCP Failover
Implementation.
19. Tuning a DHCP Service.
Network Device Configuration and Address Assignment Strategies.
Configuring Lease Lengths. Monitoring the Server.
20.
Programmable DHCP Server Customization.
Differentiating Between Clients. Controlling Address Allocation.
Client Class Options. Lease Events. Lease Variables.
21. DHCP
Clients.
The Theory of DHCP Client Operation. The Microsoft DHCP Client. The
dhcpcd DHCP Client. The pump DHCP Client. The ISC DHCP Client. The
Apple MacOS X DHCP Client.
22. Setting Up DHCP in a Small
Office.
Small Office Network Architectures. IP Address Translation. Running
a DHCP Server and Client on the Same Computer. Running the DHCP
Server on Your Firewall. Problems with DSL Routers. Configuring an
Integrated Router/Server. Configuring a WAN Port. Configuring a LAN
Port and Small Network Services.
23. Updating DNS with
DHCP.
Overview of Updating DNS with DHCP. The Motivation for Doing DNS
Updates from DHCP. The Domain Name Update Policy. Name Clashes. DNS
Update Security. Configuring the Servers. DNS Record Removal.
Debugging Problems with DNS Updates.
24. Debugging Problems with
DHCP.
The Debugging Process. Connectivity Problems. When the Server Does
Not Respond. Server DHCPNAK Message Behavior. Incorrect Option
Values. The Uniqueness of Client Identifiers. Dual-Boot Client
Systems. Duplicate IP Addresses. When a Client Fails to Get a
Reserved IP Address.
25. DHCP for IPv6.
An Introduction to IPv6. The Motivations for DHCPv6. The Design of
DHCPv6.
IV. APPENDIXES.
Appendix A. Microsoft DHCP Server Examples.
Examples 3.1, 3.2, 3.3, and 3.4. Examples 3.5 and 3.6. Example 3.7.
Examples 3.8 and 3.9. Example 3.10. Example 3.11. Examples 12.1 and
12.2. Example 13.1. Examples 14.1 through 14.6. Example 14.7.
Example 14.8. Example 14.9. Examples 14.10 and 14.11. Example
14.12. Example 14.13. Example 14.14. Examples 14.15 through 14.17.
Examples 15.1 and 15.2. Examples 15.3 through 15.7. Example 15.8.
Example 15.9. Example 15.10. Examples 15.11 and 15.12. Example
15.13. Example 15.14. Example 15.15. Example 15.16. Example 15.17.
Example 15.18. Example 15.19. Example 16.1 and 16.2. Example 16.3.
Example 16.4. Example 16.5. Example 16.6. Examples 16.7 and 16.8.
Examples 16.9, 16.10, and 16.11. Example 17.1 . Example 18.1
through 18.9. Example 19.1. Examples 20.1 through 20.14. Example
22.1. Example 22.2. Example 22.3. Example 22.4. Examples 22.5
through 22.7. Examples in Appendixes.
Appendix B. ISC DHCP Server
Configuration File Reference.
How to Use This Appendix. File Organization. The shared-network
Declaration. The subnet Declaration. The range Declaration. The
host Declaration. The pool Declaration. The class Declaration. The
subclass Declaration. The group Declaration. The option space
Declaration. The include Directive. The key Declaration. The zone
Declaration. The failover peer Declaration. Programming Statements.
Expressions. Parameter Statements. Statements That Define Values to
Send to Clients. The option Definition. The Standard DHCP
Options.
Appendix C. The DHCP Message Format.
The fixed-format Section. The variable-format Section.
Appendix
D. DHCP Options Summary.
Appendix E. Bibliography and Other Resources.
Web Resources for DHCP. RFCs Related to DHCP. Other RFCs of
Interest. Additional Reading.
Appendix F. DHCP Server and
Operating System Versions.
Choosing a DHCP Server. ISC DHCP Server Operating System
Dependencies.
Appendix G. Glossary.
Index.Promotional Information
The DHCP Handbook, Second Edition is a complete reference for
understanding DHCP, deploying and managing DHCP services, and
debugging problems with DHCP clients and servers. Chapters devoted
to failover, authentication, Windows 2000, DHCPv6, and DHCP/DNS
interaction reflect the recent updates to the standard and
addresses issues that are most pertinent to network planners and
administrators. Throughout the book, the authors are careful to
balance conceptual discussions of DHCP with detailed implementation
examples and practical advice.
About the Author
The authors of this text, Ralph Droms and Ted
Lemon, bring extensive expertise and experience with DHCP and
IP networking to this book. In this text, the authors combine their
insights to create a unique perspective on the theory and design of
the DHCP specification, as well as the practical aspects of
implementing a DHCP server and running a DHCP service.
Ralph Droms, Ph.D., organized the DHCWG with Phil Gross in 1989.
He has chaired the working group since its inception and is a key
contributor to the design and development of DHCP. Ralph is also
editor of the DHCP RFCs and continues to participate in the
evolution of DHCP. Since joining Cisco in 2000, Ralph has continued
his work on DHCP and network management. Previously, he was a
member of the Computer Science Department faculty at Bucknell
University, where he guided students through the study of TCP/IP
internetworking, operating systems, and computer architecture.
Ralph has also been a member of the computer science faculty at
Pennsylvania State University, and he was on the research staff at
IBM and Burroughs (now Unisys).
As a consultant in network architecture and infrastructure
design, Ralph has worked with large and small companies on a
variety of TCP/IP issues, including network architecture, server
strategies and configurations, and the use of DHCP, DNS, and other
technologies in network management. Ralph served as co-director of
the computer center at Bucknell, where he supervised the design and
implementation of the campuswide multiprotocol network.
Ralph lives with his wife and two daughters in Westford,
Massachusetts. You can reach him at rdroms@cisco.com.
Ted Lemon first encountered DHCP while working as a network
administrator at Digital Equipment Corporation in the early 1990s.
In 1996 Paul Vixie of the Internet Software Consortium became
concerned that there was no high-quality open-source implementation
of DHCP, and he asked Ted if he would be willing to produce one.
The ISC DHCP distribution was the result.
As part of the work of producing the ISC DHCP distribution, Ted
has been active in the IETF DHCWG since 1996. Along with Ralph,
Bernie Volz, and Jim Bound, Ted is working on a new version of DHCP
for IPv6, as well as extensions to the DHCP protocol for IPv4.
One of the important ways that open-source projects are improved
is through examination of user feedback for ways to do things
better and for common problems that users have. Ted has had a great
deal of experience helping people with common problems with the
various aspects of DHCP. His motivation in working on this book has
been to help people who need to use DHCP to learn what they need to
know to install and manage a DHCP installation without sending him
e-mail.
Ted currently works for Nominum, Inc., a leading vendor of DHCP
and DNS solutions.