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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.

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




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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.




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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,
.

[IANA.IPv4] IANA, "IPv4 Global Unicast Address Assignments",
Sep 2008, .

[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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