Network Working Group                                          G. Huston
Request for Comments: 5398                                 December 2008
Category: Informational


   Autonomous System (AS) Number Reservation for Documentation Use

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.

Copyright Notice

  Copyright (c) 2008 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.

Abstract

  To reduce the likelihood of conflict and confusion when relating
  documented examples to deployed systems, two blocks of Autonomous
  System numbers (ASNs) are reserved for use in examples in RFCs,
  books, documentation, and the like.  This document describes the
  reservation of two blocks of ASNs as reserved numbers for use in
  documentation.

1.  Introduction

  To reduce the likelihood of conflict and confusion when relating
  documented examples to deployed systems, two blocks of Autonomous
  System numbers (ASNs) are reserved for use in examples in RFCs,
  books, documentation, and the like.  This document describes the
  reservation of two blocks of ASNs as reserved numbers for use in
  documentation.

  The problems such conflicts may cause have already been encountered
  with IPv4 addresses where literal use of documented examples in a
  production environment causes address and routing conflicts with
  existing services.  Since private-use ASNs already have a context of
  use in deployed networks, these ASNs cannot be used in many example




Huston                       Informational                      [Page 1]

RFC 5398             ASN Documentation Reservation         December 2008


  situations.  In making an explicit allocation of a set of AS numbers
  reserved for documentation use, it is intended that any such
  operational problems may be avoided in the future.

  Similar considerations have been applied to IPv4 addresses
  [IANA.IPv4], IPv6 addresses [RFC3849], and domain names [RFC2606],
  and reservations have been made for similar purposes.

2.  ASNs for Documentation Use

  To allow documentation to accurately describe deployment examples,
  the use of public or private-use AS numbers is inappropriate, and a
  reserved block of AS numbers is required.  This ensures that
  documentation does not clash with public- or private-use AS numbers
  in deployed networks, and mitigates the risks to operational
  integrity of the network through inappropriate use of documentation
  to perform literal configuration of routing elements on production
  systems.

  To allow for examples relating to the transition to use of 32-bit AS
  numbers to be correctly described, a reservation of two blocks of AS
  numbers is proposed in this document.  One reserved block of 16
  contiguous AS numbers is to lie in the range of numbers that can be
  expressed as a 16-bit AS number value (i.e., values less than 65536),
  and a second reserved block of 16 contiguous AS numbers is to lie in
  the range of numbers that can only be expressed as 32-bit AS numbers
  (values greater than 65535).

3.  Operational Implications

  This assignment implies that BGP operational configurations should
  not peer with neighboring ASes that are numbered from this reserved
  AS number set.

4.  IANA Considerations

  IANA has reserved a contiguous block of 16 Autonomous System numbers
  from the unallocated number range within the "16-bit" number set for
  documentation purposes, namely 64496 - 64511, and a contiguous block
  of 16 Autonomous System numbers from the "32-bit" number set for
  documentation, namely 65536 - 65551.  These reservations have been
  documented in the IANA AS Number Registry [IANA.AS].

5.  Security Considerations

  AS number reservations do not have any direct impact on Internet
  infrastructure security.




Huston                       Informational                      [Page 2]

RFC 5398             ASN Documentation Reservation         December 2008


6.  Acknowledgements

  The author acknowledges the work of Tomoya Yoshida, Gaurab Upadhaya,
  and Philip Smith in authoring a policy proposal that was submitted to
  the APNIC Policy Process in 2008 relating to the reservation of AS
  numbers for documentation purposes.

7.  Informative References

  [IANA.AS]    IANA, "Autonomous System (AS) Numbers", Sep 2008,
               <http://www.iana.org>.

  [IANA.IPv4]  IANA, "IPv4 Global Unicast Address Assignments",
               Sep 2008, <http://www.iana.org>.

  [RFC2606]    Eastlake, D. and A. Panitz, "Reserved Top Level DNS
               Names", BCP 32, RFC 2606, June 1999.

  [RFC3849]    Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
               Reserved for Documentation", RFC 3849, July 2004.

Author's Address

  Geoff Huston

  EMail: [email protected]

























Huston                       Informational                      [Page 3]