IPv6 Unicast Address Assignment Considerations
RFC 5375

Network Working Group                                    G. Van de Velde
Request for Comments: 5375                                  C. Popoviciu
Category: Informational                                    Cisco Systems
                                                                T. Chown
                                               University of Southampton
                                                              O. Bonness
                                                                 C. Hahn
                                      T-Systems Enterprise Services GmbH
                                                           December 2008

             IPv6 Unicast Address Assignment Considerations

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

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Abstract

   One fundamental aspect of any IP communications infrastructure is its
   addressing plan.  With its new address architecture and allocation
   policies, the introduction of IPv6 into a network means that network
   designers and operators need to reconsider their existing approaches
   to network addressing.  Lack of guidelines on handling this aspect of
   network design could slow down the deployment and integration of
   IPv6.  This document aims to provide the information and
   recommendations relevant to planning the addressing aspects of IPv6
   deployments.  The document also provides IPv6 addressing case studies
   for both an enterprise and an ISP network.

Van de Velde, et al.         Informational                      [Page 1]
RFC 5375             IPv6 Addressing Considerations        December 2008

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Network-Level Addressing Design Considerations . . . . . . . .  4
     2.1.  Globally Unique Addresses  . . . . . . . . . . . . . . . .  4
     2.2.  Unique Local IPv6 Addresses  . . . . . . . . . . . . . . .  5
     2.3.  6bone Address Space  . . . . . . . . . . . . . . . . . . .  6
     2.4.  Network-Level Design Considerations  . . . . . . . . . . .  6
       2.4.1.  Sizing the Network Allocation  . . . . . . . . . . . .  8
       2.4.2.  Address Space Conservation . . . . . . . . . . . . . .  8
   3.  Subnet Prefix Considerations . . . . . . . . . . . . . . . . .  8
     3.1.  Considerations for /64 Prefixes  . . . . . . . . . . . . . 10
   4.  Allocation of the IID of an IPv6 Address . . . . . . . . . . . 10
     4.1.  Automatic EUI-64 Format Option . . . . . . . . . . . . . . 10
     4.2.  Using Privacy Extensions . . . . . . . . . . . . . . . . . 10
     4.3.  Manual/Dynamic Assignment Option . . . . . . . . . . . . . 11
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  Informative References . . . . . . . . . . . . . . . . . . . . 12
   Appendix A.  Case Studies  . . . . . . . . . . . . . . . . . . . . 16
     A.1.  Enterprise Considerations  . . . . . . . . . . . . . . . . 16
       A.1.1.  Obtaining General IPv6 Network Prefixes  . . . . . . . 16
       A.1.2.  Forming an Address (Subnet) Allocation Plan  . . . . . 17
       A.1.3.  Other Considerations . . . . . . . . . . . . . . . . . 18
       A.1.4.  Node Configuration Considerations  . . . . . . . . . . 18
     A.2.  Service Provider Considerations  . . . . . . . . . . . . . 19
       A.2.1.  Investigation of Objective Requirements for an
               IPv6 Addressing Schema of a Service Provider . . . . . 19
       A.2.2.  Exemplary IPv6 Address Allocation Plan for a
               Service Provider . . . . . . . . . . . . . . . . . . . 23
       A.2.3.  Additional Remarks . . . . . . . . . . . . . . . . . . 28
   Appendix B.  Considerations for Subnet Prefixes Different than
                /64 . . . . . . . . . . . . . . . . . . . . . . . . . 30
     B.1.  Considerations for Subnet Prefixes Shorter than /64  . . . 30
     B.2.  Considerations for Subnet Prefixes Longer than /64 . . . . 31
       B.2.1.  /126 Addresses . . . . . . . . . . . . . . . . . . . . 31
       B.2.2.  /127 Addresses . . . . . . . . . . . . . . . . . . . . 31
       B.2.3.  /128 Addresses . . . . . . . . . . . . . . . . . . . . 31
       B.2.4.  EUI-64 'u' and 'g' Bits  . . . . . . . . . . . . . . . 31