Internet Engineering Task Force (IETF) J. Mitchell Request for Comments: 6996 Microsoft Corporation BCP: 6 July 2013 Updates: 1930 Category: Best Current Practice ISSN: 2070-1721 Autonomous System (AS) Reservation for Private Use
AbstractThis document describes the reservation of Autonomous System Numbers (ASNs) that are for Private Use only, known as Private Use ASNs, and provides operational guidance on their use. This document enlarges the total space available for Private Use ASNs by documenting the reservation of a second, larger range and updates RFC 1930 by replacing Section 10 of that document. Status of This Memo This memo documents an Internet Best Current Practice. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on BCPs is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6996. Copyright Notice Copyright (c) 2013 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. 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.
Section 10 of [RFC1930]. Since the time that the range was reserved, the Border Gateway Protocol (BGP) [RFC4271] has seen deployment in new application domains, such as data center networks, which require a larger Private Use AS space. Since the introduction of "BGP Support for Four-Octet Autonomous System (AS) Number Space" [RFC6793], the total size of ASN space has increased dramatically. A larger subset of the space is available to network operators to deploy in these 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 that these ASNs, by definition, are not registered. Therefore, this RFC documents the existing Private Use ASN reservation while also introducing a second, larger range that can also be utilized. RFC2119]. Section 5 of this document. The first is part of the original 16-bit Autonomous System range previously defined in [RFC1930], and the second is a larger range out of the Four-Octet AS Number Space [RFC6793]. RFC6793] and that 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 in the four-octet AS number space. Some existing implementations that remove Private Use ASNs from the AS_PATH are known to not remove Private Use ASNs if the AS_PATH contains a mixture of Private Use and Non-Private Use ASNs. If such
implementations have not been updated to recognize the new range of ASNs in this document and a mix of old and new range Private Use ASNs exist in the AS4_PATH, these implementations will likely cease to remove any Private Use ASNs from either of the AS path attributes. Normal AS path filtering MAY also be used to prevent prefixes originating from Private Use ASNs from being advertised to the global Internet. IANA.AS]. Section 4. General BGP security considerations are discussed in [RFC4271] and [RFC4272]. Identification of the originator of a route with a Private Use ASN in the AS path would have to be done by tracking the route back to the neighboring globally unique AS in the path or by inspecting other attributes. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet Autonomous System (AS) Number Space", RFC 6793, December 2012.
[IANA.AS] IANA, "Autonomous System (AS) Numbers", <http://www.iana.org/assignments/as-numbers/>. [RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation, selection, and registration of an Autonomous System (AS)", BCP 6, RFC 1930, March 1996. [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", RFC 4272, January 2006.