IPv6 Stateless Address Autoconfiguration
RFC 1971

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Network Working Group                                         S. Thomson
Request for Comments: 1971                                      Bellcore
Category: Standards Track                                      T. Narten
                                                                     IBM
                                                             August 1996

                IPv6 Stateless Address Autoconfiguration

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

   This document specifies the steps a host takes in deciding how to
   autoconfigure its interfaces in IP version 6. The autoconfiguration
   process includes creating a link-local address and verifying its
   uniqueness on a link, determining what information should be
   autoconfigured (addresses, other information, or both), and in the
   case of addresses, whether they should be obtained through the
   stateless mechanism, the stateful mechanism, or both.  This document
   defines the process for generating a link-local address, the process
   for generating site-local and global addresses via stateless address
   autoconfiguration, and the Duplicate Address Detection procedure. The
   details of autoconfiguration using the stateful protocol are
   specified elsewhere.

Table of Contents

   1.  INTRODUCTION.............................................    2
   2.  TERMINOLOGY..............................................    4
      2.1.  Requirements........................................    7
   3.  DESIGN GOALS.............................................    8
   4.  PROTOCOL OVERVIEW........................................    9
      4.1.  Site Renumbering....................................   11
   5.  PROTOCOL SPECIFICATION...................................   11
      5.1.  Node Configuration Variables........................   12
      5.2.  Autoconfiguration-Related Variables.................   12
      5.3.  Creation of Link-Local Addresses....................   13
      5.4.  Duplicate Address Detection.........................   13
         5.4.1.  Message Validation.............................   15
         5.4.2.  Sending Neighbor Solicitation Messages.........   15
         5.4.3.  Receiving Neighbor Solicitation Messages.......   15

Thomson & Narten            Standards Track                     [Page 1]
RFC 1971       IPv6 Stateless Address Autoconfiguration      August 1996

         5.4.4.  Receiving Neighbor Advertisement Messages......   16
         5.4.5.  When Duplicate Address Detection Fails.........   16
      5.5.  Creation of Global and Site-Local Addresses.........   17
         5.5.1.  Soliciting Router Advertisements...............   17
         5.5.2.  Absence of Router Advertisements...............   17
         5.5.3.  Router Advertisement Processing................   17
         5.5.4.  Address Lifetime Expiry........................   19
      5.6.  Configuration Consistency...........................   19
   SECURITY CONSIDERATIONS......................................   19
   REFERENCES...................................................   20
   AUTHORS' ADDRESSES...........................................   21
   APPENDIX: LOOPBACK SUPPRESSION & DUPLICATE ADDRESS DETECTION.   22

1.  INTRODUCTION

   This document specifies the steps a host takes in deciding how to
   autoconfigure its interfaces in IP version 6. The autoconfiguration
   process includes creating a link-local address and verifying its
   uniqueness on a link, determining what information should be
   autoconfigured (addresses, other information, or both), and in the
   case of addresses, whether they should be obtained through the
   stateless mechanism, the stateful mechanism, or both.  This document
   defines the process for generating a link-local address, the process
   for generating site-local and global addresses via stateless address
   autoconfiguration, and the Duplicate Address Detection procedure. The
   details of autoconfiguration using the stateful protocol are
   specified elsewhere.

   IPv6 defines both a stateful and stateless address autoconfiguration
   mechanism. Stateless autoconfiguration requires no manual
   configuration of hosts, minimal (if any) configuration of routers,
   and no additional servers.  The stateless mechanism allows a host to
   generate its own addresses using a combination of locally available
   information and information advertised by routers. Routers advertise
   prefixes that identify the subnet(s) associated with a link, while
   hosts generate an "interface token" that uniquely identifies an
   interface on a subnet. An address is formed by combining the two. In