Network Working Group J.M. Mitchell
Internet-Draft Microsoft Corporation
Updates: 1930 (if approved) October 12, 2012
Intended status: Informational
Expires: April 13, 2013

Autonomous System (AS) Reservation for Private Use


This document describes the reservation of Autonomous System numbers (ASNs) that are for private use only and should not be advertised to the Internet, known as private use ASNs. This document enlarges the total space available for private use ASNs by documenting the reservation of a second, larger range and updates RFC 1930.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http:/⁠/⁠⁠drafts/⁠current/⁠.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on April 13, 2013.

Copyright Notice

Copyright (c) 2012 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:/⁠/⁠⁠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. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

1. Introduction

The original IANA reservation of Autonomous System Numbers (ASNs) for private use was a block of 1023 ASNs. This was also documented by IETF in Section 10 of [RFC1930]. Since the time when that range was reserved, BGP has seen much wider deployment in service provider, enterprise and content provider networks. The places in these networks where private use ASNs are in use include networks that are attached to the Internet, utilizing implementation specific features to remove them upon advertisement to Internet peers, and networks that are not attached to the Internet. The displacement of Frame Relay and ATM based VPNs by BGP/MPLS IP VPNs [RFC4364] has also increased the deployment of BGP to a larger number of sites, especially in networks with requirements for multi-homing or provider redundancy.

The limited size of the current range of private use ASNs has led to the re-use of private use ASNs within a single organization, requiring the use of a number of implementation specific features that manipulate the AS_PATH or remove AS_PATH based loop prevention described in Section 9 of [RFC4271]. These workarounds have increased the operational complexity of the networks since the implementations of these functions vary and are not defined in existing BGP standards.

Since the introduction of BGP Support for Four-octet AS Number Space [I-D.ietf-idr-rfc4893bis], the total size of the ASN space has increased dramatically, and a larger subset of the space should be available to network operators to deploy in private use cases. The existing range of private use ASNs is widely deployed and the ability to renumber this resource in existing networks cannot be coordinated given these ASNs by definition are not registered. Therefore this documents the existing private use ASN reservation, while also introducing a second, larger range that can also be utilized.

2. Private Use ASNs

To allow the continued growth of usage of the BGP protocol in networks that utilize private ASNs, two ranges of ASNs are reserved by this document in Section 5. The first which was previously defined in [RFC1930] out of the original 16-bit Autonomous System range and a second, larger range out of the higher part of the Four-Octet AS Number Space [I-D.ietf-idr-rfc4893bis].

3. Operational Considerations

If private use ASNs are used and prefixes are originated from these private use ASNs which are destined to the Internet, private use ASNs must be removed from the AS_PATH before being advertised to the global Internet. Operators are cautioned to ensure any filters or implementation specific features that recognize private use ASNs have been updated to recognize both ranges prior to making use of the newer, numerically higher range of private use ASNs.

4. Acknowledgements

The author would like to acknowledge Christopher Morrow and Jason Schiller for their advice on how to pursue this change. The author also thanks Brian Dickson, David Farmer, and Jeffrey Haas for their comments and suggestions.

5. IANA Considerations

[Note to IANA, NOT for publication: The IANA should update the "16-bit Autonomous System Numbers" registry to reference this RFC (when published) for the existing private use reservation. Further, to maintain consistency from an operator standpoint, it is suggested that the end of the "32-bit Autonomous System Numbers" range be reserved for Private Use, and a size of 16777215 (value to replace TBD1 below) is suggested corresponding to the range of 4278190080 (value to replace TBD2 below) to 4294967294 (value to replace TBD3 below).]

IANA has reserved, for Private Use, a contiguous block of 1023 Autonomous System numbers from the "16-bit Autonomous System Numbers" registry, namely 64512 - 65534 inclusive.

IANA has also reserved, for Private Use, a contiguous block of TBD1 Autonomous System numbers from the "32-bit Autonomous System Numbers" registry, namely TBD2 - TBD3 inclusive.

These reservations have been documented in the IANA Autonomous System Numbers Registry [IANA.AS].

6. Security Considerations

This document does not introduce any additional security concerns in regards to private use ASNs.

7. References

7.1. Normative References

[RFC4271] Rekhter, Y., Li, T. and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.
[I-D.ietf-idr-rfc4893bis] Vohra, Q and E Chen, "BGP Support for Four-octet AS Number Space", Internet-Draft draft-ietf-idr-rfc4893bis-04, July 2011.

7.2. Informative References

[IANA.AS] IANA, , "Autonomous System (AS) Numbers", October 2012.
[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation, selection, and registration of an Autonomous System (AS)", BCP 6, RFC 1930, March 1996.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006.

Author's Address

Jon Mitchell Microsoft Corporation 12012 Sunset Hills Road Reston, VA 20190 USA EMail:

Table of Contents