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.

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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

   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.

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: gih@apnic.net