IP Version 6 Addressing Architecture
RFC 4291

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Network Working Group                                          R. Hinden
Request for Comments: 4291                                         Nokia
Obsoletes: 3513                                               S. Deering
Category: Standards Track                                  Cisco Systems
                                                           February 2006

                  IP Version 6 Addressing Architecture

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.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This specification defines the addressing architecture of the IP
   Version 6 (IPv6) protocol.  The document includes the IPv6 addressing
   model, text representations of IPv6 addresses, definition of IPv6
   unicast addresses, anycast addresses, and multicast addresses, and an
   IPv6 node's required addresses.

   This document obsoletes RFC 3513, "IP Version 6 Addressing
   Architecture".

Hinden                      Standards Track                     [Page 1]
RFC 4291              IPv6 Addressing Architecture         February 2006

Table of Contents

   1. Introduction ....................................................2
   2. IPv6 Addressing .................................................2
      2.1. Addressing Model ...........................................3
      2.2. Text Representation of Addresses ...........................4
      2.3. Text Representation of Address Prefixes ....................5
      2.4. Address Type Identification ................................6
      2.5. Unicast Addresses ..........................................6
           2.5.1. Interface Identifiers ...............................7
           2.5.2. The Unspecified Address .............................9
           2.5.3. The Loopback Address ................................9
           2.5.4. Global Unicast Addresses ............................9
           2.5.5. IPv6 Addresses with Embedded IPv4 Addresses ........10
           2.5.6. Link-Local IPv6 Unicast Addresses ..................11
           2.5.7. Site-Local IPv6 Unicast Addresses ..................11
      2.6. Anycast Addresses .........................................12
           2.6.1. Required Anycast Address ...........................12
      2.7. Multicast Addresses .......................................13
           2.7.1. Pre-Defined Multicast Addresses ....................15
      2.8. A Node's Required Addresses ...............................17
   3. Security Considerations ........................................18
   4. IANA Considerations ............................................18
   5. Acknowledgements ...............................................18
   6. References .....................................................18
      6.1. Normative References ......................................18
      6.2. Informative References ....................................18
   Appendix A: Creating Modified EUI-64 Format Interface Identifiers .20
   Appendix B: Changes from RFC 3513 .................................22

1.  Introduction

   This specification defines the addressing architecture of the IP
   Version 6 protocol.  It includes the basic formats for the various
   types of IPv6 addresses (unicast, anycast, and multicast).

2.  IPv6 Addressing

   IPv6 addresses are 128-bit identifiers for interfaces and sets of
   interfaces (where "interface" is as defined in Section 2 of [IPV6]).
   There are three types of addresses:

    Unicast:   An identifier for a single interface.  A packet sent to a
               unicast address is delivered to the interface identified
               by that address.

Hinden                      Standards Track                     [Page 2]
RFC 4291              IPv6 Addressing Architecture         February 2006

    Anycast:   An identifier for a set of interfaces (typically
               belonging to different nodes).  A packet sent to an
               anycast address is delivered to one of the interfaces
               identified by that address (the "nearest" one, according
               to the routing protocols' measure of distance).

    Multicast: An identifier for a set of interfaces (typically
               belonging to different nodes).  A packet sent to a
               multicast address is delivered to all interfaces
               identified by that address.

   There are no broadcast addresses in IPv6, their function being
   superseded by multicast addresses.

   In this document, fields in addresses are given a specific name, for
   example, "subnet".  When this name is used with the term "ID" for