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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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 Copyright (c) 2008 IETF Trust and the persons identified as the
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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

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: gih@apnic.net

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