Dynamic Host Configuration Protocol
RFC 1541

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Network Working Group                                           R. Droms
Request for Comments: 1541                           Bucknell University
Obsoletes: 1531                                             October 1993
Category: Standards Track

                  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].  Due to some errors introduced into RFC
   1531 in the editorial process, this memo is reissued as RFC 1541.

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

Droms                                                           [Page 1]
RFC 1541          Dynamic Host Configuration Protocol       October 1993

   4.1 Constructing and sending DHCP messages. . . . . . . . . . . . 21
   4.2 DHCP server administrative controls . . . . . . . . . . . . . 23
   4.3 DHCP server behavior. . . . . . . . . . . . . . . . . . . . . 24
   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