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Autonomous System (AS) Reservation for Private Use

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 6996.
Author Jon Mitchell
Last updated 2013-04-25 (Latest revision 2013-04-12)
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Document shepherd Susan Hares
Shepherd write-up Show Last changed 2013-02-07
IESG IESG state Became RFC 6996 (Best Current Practice)
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD Stewart Bryant
Send notices to,
IANA IANA review state IANA OK - Actions Needed
Network Working Group                                        J. Mitchell
Internet-Draft                                     Microsoft Corporation
Updates: 1930 (if approved)                               April 12, 2013
Intended status: Best Current Practice
Expires: October 14, 2013

           Autonomous System (AS) Reservation for Private Use


   This document describes the reservation of Autonomous System numbers
   (ASNs) that are for Private Use only and MUST NOT be advertised to
   the Internet, known as Private Use ASNs.  This document enlarges the
   total space available for Private Use ASNs by documenting the
   reservation of a second, larger range and updates RFC 1930 by
   replacing Section 10.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 14, 2013.

Copyright Notice

   Copyright (c) 2013 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
   ( 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

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Introduction

   The original IANA reservation of Autonomous System Numbers (ASNs) for
   Private Use was a block of 1023 ASNs.  This was also documented by
   IETF in Section 10 of [RFC1930].  Since the time when that range was
   reserved, Border Gateway Protocol (BGP), documented in [RFC4271], has
   seen deployment in new application domains, such as datacenter
   networks, which require a larger Private Use AS Space.

   Since the introduction of BGP Support for Four-octet AS Number Space
   [RFC6793], the total size of the ASN space has increased
   dramatically, and a larger subset of the space should be available to
   network operators to deploy in these Private Use cases.  The existing
   range of Private Use ASNs is widely deployed and the ability to
   renumber this resource in existing networks cannot be coordinated
   given these ASNs by definition are not registered.  Therefore this
   documents the existing Private Use ASN reservation, while also
   introducing a second, larger range that can also be utilized.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  Private Use ASNs

   To allow the continued growth of usage of the BGP protocol in new
   network applications that utilize Private Use ASNs, two ranges of
   ASNs are reserved by this document in Section 6.  The first, which
   was previously defined in [RFC1930] out of the original 16-bit
   Autonomous System range, and a second, larger range out of the higher
   part of the Four-Octet AS Number Space [RFC6793].

4.  Operational Considerations

   If Private Use ASNs are used and prefixes are originated from these
   ASNs, which are destined to the Internet, Private Use ASNs MUST be
   removed from the AS_PATH before being advertised to the global
   Internet.  Operators are cautioned to ensure any implementation
   specific features that recognize Private Use ASNs have been updated
   to recognize both ranges prior to making use of the newer,
   numerically higher range of Private Use ASNs.  Some existing
   implementations that remove Private Use ASNs from the AS_PATH may
   fail to remove Private Use ASNs if the AS_PATH contains a mixture of

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   Private Use and Non-Private Use ASNs.  If such implementations have
   not been updated to recognize the new range of ASNs in this document
   and a mix of old and new range Private Use ASNs exist in the path,
   these implementations may cease to remove any Private Use ASNs from
   the AS_PATH.  Normal AS_PATH filtering may be used to prevent
   prefixes originating from Private Use ASNs from being advertised to
   the global Internet.  Using AS_PATH filtering to filter the new range
   of Private Use ASNs on a network may also mitigate the leaking of
   Private Use ASNs to the global Internet in certain cases.  These
   cases include the case where a network is reliant on AS_PATH
   manipulation features that have not been updated to recognize the new
   range as described above.

5.  Acknowledgements

   The author would like to acknowledge Christopher Morrow, Jason
   Schiller, and John Scudder for their advice on how to pursue this
   change.  The author would also like to thank Brian Dickson, David
   Farmer, Jeffrey Haas, Nick Hilliard, Warren Kumari, and Jeff Wheeler
   for their comments and suggestions.

6.  IANA Considerations

   [Note to IANA, this paragraph to be removed upon publication: The
   IANA should update the "16-bit Autonomous System Numbers" registry to
   reference this RFC for the existing Private Use reservation.  The end
   of the "32-bit Autonomous System Numbers" range will be reserved for
   Private Use, and a size of 94,967,295 (value to replace TBD1 below)
   corresponding to the range of 4200000000 (value to replace TBD2
   below) to 4294967294 (value to replace TBD3 below).  Text after this
   sentence should be published in the document.]

   IANA has reserved, for Private Use, a contiguous block of 1023
   Autonomous System numbers from the "16-bit Autonomous System Numbers"
   registry, namely 64512 - 65534 inclusive.

   IANA has also reserved, for Private Use, a contiguous block of TBD1
   Autonomous System numbers from the "32-bit Autonomous System Numbers"
   registry, namely TBD2 - TBD3 inclusive.

   These reservations have been documented in the IANA Autonomous System
   Numbers Registry [IANA.AS].

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7.  Security Considerations

   This document does not introduce any additional security concerns in
   regards to Private Use ASNs.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC6793]  Vohra, Q. and E. Chen, "BGP Support for Four-Octet
              Autonomous System (AS) Number Space", RFC 6793, December

8.2.  Informative References

   [IANA.AS]  IANA, , "Autonomous System (AS) Numbers", April 2013,

   [RFC1930]  Hawkinson, J. and T. Bates, "Guidelines for creation,
              selection, and registration of an Autonomous System (AS)",
              BCP 6, RFC 1930, March 1996.

Author's Address

   Jon Mitchell
   Microsoft Corporation
   1 Microsoft Way
   Redmond, WA  98052


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