IPv6 Stateless Address Autoconfiguration
RFC 4862

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Network Working Group                                         S. Thomson
Request for Comments: 4862                                         Cisco
Obsoletes: 2462                                                T. Narten
Category: Standards Track                                            IBM
                                                               T. Jinmei
                                                                 Toshiba
                                                          September 2007

                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 generating a link-local address, generating global
   addresses via stateless address autoconfiguration, and the Duplicate
   Address Detection procedure to verify the uniqueness of the addresses
   on a link.

Thomson, et al.             Standards Track                     [Page 1]
RFC 4862        IPv6 Stateless Address Autoconfiguration  September 2007

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  7
   3.  Design Goals . . . . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Protocol Overview  . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Site Renumbering . . . . . . . . . . . . . . . . . . . . .  9
   5.  Protocol Specification . . . . . . . . . . . . . . . . . . . . 10
     5.1.  Node Configuration Variables . . . . . . . . . . . . . . . 10
     5.2.  Autoconfiguration-Related Structures . . . . . . . . . . . 11
     5.3.  Creation of Link-Local Addresses . . . . . . . . . . . . . 11
     5.4.  Duplicate Address Detection  . . . . . . . . . . . . . . . 12
       5.4.1.  Message Validation . . . . . . . . . . . . . . . . . . 14
       5.4.2.  Sending Neighbor Solicitation Messages . . . . . . . . 14
       5.4.3.  Receiving Neighbor Solicitation Messages . . . . . . . 15
       5.4.4.  Receiving Neighbor Advertisement Messages  . . . . . . 16
       5.4.5.  When Duplicate Address Detection Fails . . . . . . . . 17
     5.5.  Creation of Global Addresses . . . . . . . . . . . . . . . 17
       5.5.1.  Soliciting Router Advertisements . . . . . . . . . . . 18
       5.5.2.  Absence of Router Advertisements . . . . . . . . . . . 18
       5.5.3.  Router Advertisement Processing  . . . . . . . . . . . 18
       5.5.4.  Address Lifetime Expiry  . . . . . . . . . . . . . . . 20
     5.6.  Configuration Consistency  . . . . . . . . . . . . . . . . 21
     5.7.  Retaining Configured Addresses for Stability . . . . . . . 22
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 22
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 23
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 23
   Appendix A.  Loopback Suppression and Duplicate Address
                Detection . . . . . . . . . . . . . . . . . . . . . . 25
   Appendix B.  Changes since RFC 1971  . . . . . . . . . . . . . . . 26
   Appendix C.  Changes since RFC 2462  . . . . . . . . . . . . . . . 27

Thomson, et al.             Standards Track                     [Page 2]
RFC 4862        IPv6 Stateless Address Autoconfiguration  September 2007

1.  Introduction

   This document specifies the steps a host takes in deciding how to
   autoconfigure its interfaces in IP version 6 (IPv6).  The
   autoconfiguration process includes generating a link-local address,
   generating global addresses via stateless address autoconfiguration,
   and the Duplicate Address Detection procedure to verify the
   uniqueness of the addresses on a link.

   The IPv6 stateless autoconfiguration mechanism 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 identifier" that uniquely identifies an
   interface on a subnet.  An address is formed by combining the two.
   In the absence of routers, a host can only generate link-local