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Network Working Group                                     D. EastlakeRequest for Comments: 2606                                  A. PanitzBCP: 32                                                     June 1999Category: Best Current PracticeReserved Top Level DNS NamesStatus of this Memo   This document specifies an Internet Best Current Practices for the   Internet Community, and requests discussion and suggestions for   improvements.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (1999).  All Rights Reserved.Abstract   To reduce the likelihood of conflict and confusion, a few top level   domain names are reserved for use in private testing, as examples in   documentation, and the like.  In addition, a few second level domain   names reserved for use as examples are documented.Table of Contents1. Introduction............................................12. TLDs for Testing, & Documentation Examples..............23. Reserved Example Second Level Domain Names..............24. IANA Considerations.....................................35. Security Considerations.................................3   References.................................................3   Authors' Addresses.........................................4   Full Copyright Statement...................................51. Introduction   The global Internet Domain Name System is documented in [RFC 1034,   1035, 1591] and numerous additional Requests for Comment.  It defines   a tree of names starting with root, ".", immediately below which are   top level domain names such as ".com" and ".us". Below top level   domain names there are normally additional levels of names.Eastlake & Panitz        Best Current Practice                  [Page 1]

RFC 2606              Reserved Top Level DNS Names             June 19992. TLDs for Testing, & Documentation Examples   There is a need for top level domain (TLD) names that can be used for   creating names which, without fear of conflicts with current or   future actual TLD names in the global DNS, can be used for private   testing of existing DNS related code, examples in documentation, DNS   related experimentation, invalid DNS names, or other similar uses.   For example, without guidance, a site might set up some local   additional unused top level domains for testing of its local DNS code   and configuration. Later, these TLDs might come into actual use on   the global Internet.  As a result, local attempts to reference the   real data in these zones could be thwarted by the local test   versions.  Or test or example code might be written that accesses a   TLD that is in use with the thought that the test code would only be   run in a restricted testbed net or the example never actually run.   Later, the test code could escape from the testbed or the example be   actually coded and run on the Internet. Depending on the nature of   the test or example, it might be best for it to be referencing a TLD   permanently reserved for such purposes.   To safely satisfy these needs, four domain names are reserved as   listed and described below.                   .test                .example                .invalid              .localhost      ".test" is recommended for use in testing of current or new DNS      related code.      ".example" is recommended for use in documentation or as examples.      ".invalid" is intended for use in online construction of domain      names that are sure to be invalid and which it is obvious at a      glance are invalid.      The ".localhost" TLD has traditionally been statically defined in      host DNS implementations as having an A record pointing to the      loop back IP address and is reserved for such use.  Any other use      would conflict with widely deployed code which assumes this use.3. Reserved Example Second Level Domain Names   The Internet Assigned Numbers Authority (IANA) also currently has the   following second level domain names reserved which can be used as   examples.Eastlake & Panitz        Best Current Practice                  [Page 2]

RFC 2606              Reserved Top Level DNS Names             June 1999        example.com        example.net        example.org4. IANA Considerations   IANA has agreed to the four top level domain name reservations   specified in this document and will reserve them for the uses   indicated.5. Security Considerations   Confusion and conflict can be caused by the use of a current or   future top level domain name in experimentation or testing, as an   example in documentation, to indicate invalid names, or as a synonym   for the loop back address.  Test and experimental software can escape   and end up being run against the global operational DNS.  Even   examples used "only" in documentation can end up being coded and   released or cause conflicts due to later real use and the possible   acquisition of intellectual property rights in such "example" names.   The reservation of several top level domain names for these purposes   will minimize such confusion and conflict.References   [RFC 1034] Mockapetris, P., "Domain names - concepts and facilities",              STD 13,RFC 1034, November 1987.   [RFC 1035] Mockapetris, P., "Domain names - implementation and              specification", STD 13,RFC 1035, November 1987.   [RFC 1591] Postel, J., "Domain Name System Structure and Delegation",RFC 1591, March 1994.Eastlake & Panitz        Best Current Practice                  [Page 3]

RFC 2606              Reserved Top Level DNS Names             June 1999Authors' Addresses   Donald E. Eastlake 3rd   IBM   65 Shindegan Hill Road, RR #1   Carmel, NY 10512   Phone: +1 914-276-1668(h)          +1 914-784-7913(w)   FAX:   +1 914-784-3833(3)   EMail: dee3@us.ibm.com   Aliza R. Panitz   500 Stamford Dr. No. 310   Newark, DE 19711 USA   Phone: +1 302-738-1554   EMail: buglady@fuschia.netEastlake & Panitz        Best Current Practice                  [Page 4]

RFC 2606              Reserved Top Level DNS Names             June 1999Full Copyright Statement   Copyright (C) The Internet Society (1999).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Eastlake & Panitz        Best Current Practice                  [Page 5]