Dynamic Host Configuration Protocol
RFC 1531

Document Type RFC - Proposed Standard (October 1993; Errata)
Obsoleted by RFC 1541
Last updated 2013-03-02
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Network Working Group                                           R. Droms
Request for Comments: 1531                           Bucknell University
Category: Standards Track                                   October 1993

                  Dynamic Host Configuration Protocol

Status of this memo

   This RFC specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" for the standardization state and status
   of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Dynamic Host Configuration Protocol (DHCP) provides a framework
   for passing configuration information to hosts on a TCP/IP network.
   DHCP is based on the Bootstrap Protocol (BOOTP) [7], adding the
   capability of automatic allocation of reusable network addresses and
   additional configuration options [19].  DHCP captures the behavior of
   BOOTP relay agents [7, 23], and DHCP participants can interoperate
   with BOOTP participants [9].

Table of Contents

   1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .  2
   1.1 Related Work. . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.2 Problem definition and issues . . . . . . . . . . . . . . . .  4
   1.3 Requirements. . . . . . . . . . . . . . . . . . . . . . . . .  5
   1.4 Terminology . . . . . . . . . . . . . . . . . . . . . . . . .  6
   1.5 Design goals. . . . . . . . . . . . . . . . . . . . . . . . .  6
   2. Protocol Summary . . . . . . . . . . . . . . . . . . . . . . .  8
   2.1 Configuration parameters repository . . . . . . . . . . . . . 10
   2.2 Dynamic allocation of network addresses . . . . . . . . . . . 11
   3. The Client-Server Protocol . . . . . . . . . . . . . . . . . . 11
   3.1 Client-server interaction - allocating a network address. . . 12
   3.2 Client-server interaction - reusing a  previously allocated
       network address . . . . . . . . . . . . . . . . . . . . . . . 17
   3.3 Interpretation and representation of time values. . . . . . . 19
   3.4 Host parameters in DHCP . . . . . . . . . . . . . . . . . . . 19
   3.5 Use of DHCP in clients with multiple interfaces . . . . . . . 20
   3.6 When clients should use DHCP. . . . . . . . . . . . . . . . . 20
   4. Specification of the DHCP client-server protocol . . . . . . . 21
   4.1 Constructing and sending DHCP messages. . . . . . . . . . . . 21
   4.2 DHCP server administrative controls . . . . . . . . . . . . . 23
   4.3 DHCP server behavior. . . . . . . . . . . . . . . . . . . . . 24

Droms                                                           [Page 1]
RFC 1531          Dynamic Host Configuration Protocol       October 1993

   4.3.1 DHCPDISCOVER message. . . . . . . . . . . . . . . . . . . . 24
   4.3.2 DHCPREQUEST message . . . . . . . . . . . . . . . . . . . . 27
   4.3.3 DHCPDECLINE message . . . . . . . . . . . . . . . . . . . . 29
   4.3.4 DHCPRELEASE message . . . . . . . . . . . . . . . . . . . . 29
   4.4 DHCP client behavior. . . . . . . . . . . . . . . . . . . . . 29
   4.4.1 Initialization and allocation of network address. . . . . . 29
   4.4.2 Initialization with known network address . . . . . . . . . 33
   4.4.3 Initialization with a known DHCP server address . . . . . . 34
   4.4.4 Reacquisition and expiration. . . . . . . . . . . . . . . . 34
   4.4.5 DHCPRELEASE . . . . . . . . . . . . . . . . . . . . . . . . 35
   5. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 35
   6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 36
   7. Security Considerations. . . . . . . . . . . . . . . . . . . . 37
   8. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 38
   A. Host Configuration Parameters  . . . . . . . . . . . . . . . . 39

List of Figures

   1. Format of a DHCP message . . . . . . . . . . . . . . . . . . .  9
   2. Format of the 'flags' field. . . . . . . . . . . . . . . . . . 10
   3. Timeline diagram of messages exchanged between DHCP client and
      servers when allocating a new network address. . . . . . . . . 15
   4. Timeline diagram of messages exchanged between DHCP client and
      servers when reusing a previously allocated network address. . 18
   5. State-transition diagram for DHCP clients. . . . . . . . . . . 31

List of Tables

   1. Description of fields in a DHCP message. . . . . . . . . . . . 14
   2. DHCP messages. . . . . . . . . . . . . . . . . . . . . . . . . 16
   3. Fields and options used by DHCP servers. . . . . . . . . . . . 25
   4. Fields and options used by DHCP clients. . . . . . . . . . . . 32

1. Introduction

   The Dynamic Host Configuration Protocol (DHCP) provides configuration
   parameters to Internet hosts.  DHCP consists of two components: a
   protocol for delivering host-specific configuration parameters from a
   DHCP server to a host and a mechanism for allocation of network
   addresses to hosts.
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