Dynamic Host Configuration Protocol
RFC 2131

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 08

Network Working Group                                           R. Droms
Request for Comments: 2131                           Bucknell University
Obsoletes: 1541                                               March 1997
Category: Standards Track

                  Dynamic Host Configuration Protocol

Status of this memo

   This document 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" (STD 1) 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 TCPIP 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, 21], and DHCP participants can interoperate
   with BOOTP participants [9].

Table of Contents

   1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .  2
   1.1 Changes to RFC1541. . . . . . . . . . . . . . . . . . . . . .  3
   1.2 Related Work. . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.3 Problem definition and issues . . . . . . . . . . . . . . . .  4
   1.4 Requirements. . . . . . . . . . . . . . . . . . . . . . . . .  5
   1.5 Terminology . . . . . . . . . . . . . . . . . . . . . . . . .  6
   1.6 Design goals. . . . . . . . . . . . . . . . . . . . . . . . .  6
   2.  Protocol Summary. . . . . . . . . . . . . . . . . . . . . . .  8
   2.1 Configuration parameters repository . . . . . . . . . . . . . 11
   2.2 Dynamic allocation of network addresses . . . . . . . . . . . 12
   3.  The Client-Server Protocol. . . . . . . . . . . . . . . . . . 13
   3.1 Client-server interaction - allocating a network address. . . 13
   3.2 Client-server interaction - reusing a  previously allocated
       network address . . . . . . . . . . . . . . . . . . . . . . . 17
   3.3 Interpretation and representation of time values. . . . . . . 20
   3.4 Obtaining parameters with externally configured network
       address . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
   3.5 Client parameters in DHCP . . . . . . . . . . . . . . . . . . 21
   3.6 Use of DHCP in clients with multiple interfaces . . . . . . . 22
   3.7 When clients should use DHCP. . . . . . . . . . . . . . . . . 22
   4.  Specification of the DHCP client-server protocol. . . . . . . 22

Droms                       Standards Track                     [Page 1]
RFC 2131          Dynamic Host Configuration Protocol         March 1997

   4.1 Constructing and sending DHCP messages. . . . . . . . . . . . 22
   4.2 DHCP server administrative controls . . . . . . . . . . . . . 25
   4.3 DHCP server behavior. . . . . . . . . . . . . . . . . . . . . 26
   4.4 DHCP client behavior. . . . . . . . . . . . . . . . . . . . . 34
   5.  Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . .42
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . .42
   7.  Security Considerations. . . . . . . . . . . . . . . . . . . .43
   8.  Author's Address . . . . . . . . . . . . . . . . . . . . . . .44
   A.  Host Configuration Parameters  . . . . . . . . . . . . . . . .45
List of Figures
   1. Format of a DHCP message . . . . . . . . . . . . . . . . . . .  9
   2. Format of the 'flags' field. . . . . . . . . . . . . . . . . . 11
   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. . . . . . . . . . . 34
List of Tables
   1. Description of fields in a DHCP message. . . . . . . . . . . . 10
   2. DHCP messages. . . . . . . . . . . . . . . . . . . . . . . . . 14
   3. Fields and options used by DHCP servers. . . . . . . . . . . . 28
   4. Client messages from various states. . . . . . . . . . . . . . 33
   5. Fields and options used by DHCP clients. . . . . . . . . . . . 37

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.

   DHCP is built on a client-server model, where designated DHCP server
   hosts allocate network addresses and deliver configuration parameters
   to dynamically configured hosts.  Throughout the remainder of this
   document, the term "server" refers to a host providing initialization
   parameters through DHCP, and the term "client" refers to a host