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Network Working Group                                          G. HustonRequest for Comments: 5398                                 December 2008Category: InformationalAutonomous System (AS) Number Reservation for Documentation UseStatus 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 toBCP 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 exampleHuston                       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 20086.  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.netHuston                       Informational                      [Page 3]