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
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: email@example.com