IP Version 6 Addressing Architecture
RFC 1884

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Network Working Group                       R. Hinden, Ipsilon Networks
Request for Comments: 1884                       S. Deering, Xerox PARC
Category: Standards Track                                       Editors
                                                          December 1995

                  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.

Abstract

   This specification defines the addressing architecture of the IP
   Version 6 protocol [IPV6].  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 nodes required addresses.

Hinden & Deering            Standards Track                     [Page 1]
RFC 1884              IPv6 Addressing Architecture         December 1995

Table of Contents

   1. Introduction................................................3

   2. IPv6 Addressing.............................................3
      2.1 Addressing Model........................................4
      2.2 Text Representation of Addresses........................4
      2.3 Address Type Representation.............................5
      2.4 Unicast Addresses.......................................7
        2.4.1 Unicast Address Example.............................8
        2.4.2 The Unspecified Address.............................9
        2.4.3 The Loopback Address................................9
        2.4.4 IPv6 Addresses with Embedded IPv4 Addresses.........9
        2.4.5 NSAP Addresses......................................10
        2.4.6 IPX Addresses.......................................10
        2.4.7 Provider-Based Global Unicast Addresses.............10
        2.4.8 Local-use IPv6 Unicast Addresses....................11
      2.5 Anycast Addresses.......................................12
        2.5.1 Required Anycast Address............................13
      2.6 Multicast Addresses.....................................14
        2.6.1 Pre-Defined Multicast Addresses.....................15
      2.7 A Node's Required Addresses.............................17

   REFERENCES.....................................................18

   SECURITY CONSIDERATIONS........................................18

   DOCUMENT EDITOR'S ADDRESSES....................................18

Hinden & Deering            Standards Track                     [Page 2]
RFC 1884              IPv6 Addressing Architecture         December 1995

1.0 INTRODUCTION

   This specification defines the addressing architecture of the IP
   Version 6 protocol.  It includes a detailed description of the
   currently defined address formats for IPv6 [IPV6].

   The editors would like to acknowledge the contributions of Paul
   Francis, Jim Bound, Brian Carpenter, Deborah Estrin, Peter Ford, Bob
   Gilligan, Christian Huitema, Tony Li, Greg Minshall, Erik Nordmark,
   Yakov Rekhter, Bill Simpson, and Sue Thomson.

2.0 IPv6 ADDRESSING

   IPv6 addresses are 128-bit identifiers for interfaces and sets of
   interfaces.  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.

       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 "subscriber".  When this name is used with the term "ID" for
   identifier after the name (e.g., "subscriber ID"), it refers to the
   contents of the named field.  When it is used with the term "prefix"
   (e.g., "subscriber prefix") it refers to all of the address up to and
   including this field.

   In IPv6, all zeros and all ones are legal values for any field,
   unless specifically excluded.  Specifically, prefixes may contain
   zero-valued fields or end in zeros.