Issues Associated with Designating Additional Private IPv4 Address Space
RFC 6319

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Internet Engineering Task Force (IETF)                        M. Azinger
Request for Comments: 6319                       Frontier Communications
Category: Informational                                      Corporation
ISSN: 2070-1721                                                L. Vegoda
                                                                   ICANN
                                                               July 2011

                         Issues Associated with
           Designating Additional Private IPv4 Address Space

Abstract

   When a private network or internetwork grows very large, it is
   sometimes not possible to address all interfaces using private IPv4
   address space because there are not enough addresses.  This document
   describes the problems faced by those networks, the available
   options, and the issues involved in assigning a new block of private
   IPv4 address space.

   While this informational document does not make a recommendation for
   action, it documents the issues surrounding the various options that
   have been considered.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6319.

Azinger & Vegoda              Informational                     [Page 1]
RFC 6319                 Additional Private IPv4               July 2011

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Large Networks . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Non-Unique Addresses . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Subscriber Use Network Address Translation . . . . . . . .  3
     3.2.  Carrier-Grade Network Address Translation  . . . . . . . .  4
   4.  Available Options  . . . . . . . . . . . . . . . . . . . . . .  4
     4.1.  IPv6 Options . . . . . . . . . . . . . . . . . . . . . . .  4
       4.1.1.  Unique Globally Scoped IPv6 Unicast Addresses  . . . .  4
       4.1.2.  Unique Local IPv6 Unicast Addresses  . . . . . . . . .  5
     4.2.  IPv4 Options . . . . . . . . . . . . . . . . . . . . . . .  5
       4.2.1.  Address Transfers or Leases from Organizations
               with Available Address Space . . . . . . . . . . . . .  5
       4.2.2.  Using Unannounced Address Space Allocated to
               Another Organization . . . . . . . . . . . . . . . . .  5
       4.2.3.  Unique IPv4 Space Registered by an RIR . . . . . . . .  6
   5.  Options and Consequences for Defining New Private Use Space  .  6
     5.1.  Redefining Existing Unicast Space as Private Address
           Space  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     5.2.  Unique IPv4 Space Shared by a Group of Operators . . . . .  7
     5.3.  Potential Consequences of Not Redefining Existing
           Unicast Space as Private Address Space . . . . . . . . . .  8
     5.4.  Redefining Future Use Space as Unicast Address Space . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     7.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 12

Azinger & Vegoda              Informational                     [Page 2]
RFC 6319                 Additional Private IPv4               July 2011

1.  Introduction

   [RFC1918] sets aside three blocks of IPv4 address space for use in
   private networks: 192.168.0.0/16, 172.16.0.0/12 and 10.0.0.0/8.
   These blocks can be used simultaneously in multiple, separately
   managed networks without registration or coordination with IANA or