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Internet Engineering Task Force (IETF)                         S. VenaasRequest for Comments: 6676                                     R. ParekhCategory: Informational                                  G. Van de VeldeISSN: 2070-1721                                            Cisco Systems                                                                T. Chown                                               University of Southampton                                                              M. Eubanks                                                 Iformata Communications                                                             August 2012Multicast Addresses for DocumentationAbstract   This document discusses which multicast addresses should be used for   documentation purposes and reserves multicast addresses for such use.   Some multicast addresses are derived from AS numbers or unicast   addresses.  This document also explains how these can be used for   documentation purposes.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   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).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6676.Venaas, et al.                Informational                     [Page 1]

RFC 6676          Multicast Addresses for Documentation      August 2012Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Table of Contents1. Introduction ....................................................22. IPv4 Multicast Documentation Addresses ..........................32.1. Administratively Scoped IPv4 Multicast Addresses ...........32.2. GLOP Multicast Addresses ...................................32.3. Unicast Prefix-Based IPv4 Multicast Addresses ..............43. IPv6 Multicast Documentation Addresses ..........................43.1. Unicast Prefix-Based IPv6 Multicast Addresses ..............53.2. Embedded-RP IPv6 Multicast Addresses .......................54. Security Considerations .........................................55. IANA Considerations .............................................56. Acknowledgments .................................................67. Informative References ..........................................61.  Introduction   It is often useful in documentation, IETF documents, etc., to provide   examples containing IP multicast addresses.  For documentation where   examples of general purpose multicast addresses are needed, one   should use multicast addresses that will never be assigned or in   actual use.  There is a risk that addresses used in examples may   accidentally be used.  It is then important that the same addresses   not be used by other multicast applications or services.  It may also   be beneficial to filter out such addresses from multicast signalling   and to filter out multicast data sent to such addresses.   For unicast, there are both IPv4 and IPv6 addresses reserved for this   purpose; see [RFC5737] and [RFC3849], respectively.  This document   reserves multicast addresses for this same purpose.Venaas, et al.                Informational                     [Page 2]

RFC 6676          Multicast Addresses for Documentation      August 2012   There are also some multicast addresses that are derived from AS   numbers or unicast addresses.  For examples where such addresses are   desired, one should derive them from the AS numbers and unicast   addresses reserved for documentation purposes.  This document also   discusses the use of these.2.  IPv4 Multicast Documentation Addresses   For Any-Source Multicast (ASM), the IPv4 multicast addresses   allocated for documentation purposes are 233.252.0.0 - 233.252.0.255   (233.252.0.0/24).   For Source-Specific Multicast (SSM), it is less important which   multicast addresses are used, since a host/application joins a   channel identified by both source and group.  Any source addresses   used in SSM examples should be unicast addresses reserved for   documentation purposes.  There are three unicast address ranges   provided for documentation use in [RFC5737].  The ranges are   192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24.   Sometimes one wants to give examples where a specific type of address   is desired.  For example, for text about multicast scoping, one might   want the examples to use addresses that are to be used for   administrative scoping.  See below for guidance on how to construct   specific types of example addresses.2.1.  Administratively Scoped IPv4 Multicast Addresses   Administratively scoped IPv4 multicast addresses [RFC2365] are   reserved for scoped multicast.  They can be used within a site or an   organization.  Apart from a small set of scope-relative addresses,   these addresses are not assigned.  The high order /24 in every scope   is reserved for relative assignments.  A relative assignment is an   integer offset from the highest address in the scope and represents   an IPv4 address.  For documentation purposes, the integer offset is   10.  This provides one multicast address per scope.   For example in the Local Scope 239.255.0.0/16, the multicast address   for documentation purposes is 239.255.255.245.2.2.  GLOP Multicast Addresses   GLOP [RFC3180] is a method for deriving IPv4 multicast group   addresses from 16-bit AS numbers.  For examples where GLOP addresses   are desired, the addresses should be derived from the AS numbers   reserved for documentation use.Venaas, et al.                Informational                     [Page 3]

RFC 6676          Multicast Addresses for Documentation      August 2012   The 16-bit AS numbers reserved for documentation use in [RFC5398] are   64496 - 64511.  By use of [RFC3180], we then get 16 /24 multicast   prefixes for documentation use.  The first one is 233.251.240.0/24,   and the last one is 233.251.255.0/24.2.3.  Unicast Prefix-Based IPv4 Multicast Addresses   IPv4 multicast addresses can be derived from IPv4 unicast prefixes,   see [RFC6034].  For examples where this type of address is desired,   the addresses should be derived from the unicast addresses reserved   for documentation purposes, see [RFC5737].   There are three unicast address ranges provided for documentation use   in [RFC5737].  The ranges are 192.0.2.0/24, 198.51.100.0/24, and   203.0.113.0/24.  Using [RFC6034], this leaves the unicast prefix-   based IPv4 multicast addresses 234.192.0.2, 234.198.51.100, and   234.203.0.113.3.  IPv6 Multicast Documentation Addresses   For Any-Source Multicast (ASM), the IPv6 multicast addresses   allocated for documentation purposes are FF0X::DB8:0:0/96.  This is a   /96 prefix so that it can be used with group IDs, according to the   allocation guidelines in [RFC3307].  Also note that for these   addresses, the transient flag, or "T-flag" as defined in [RFC4291],   is zero.  This is because they are permanently assigned.  There can   be no permanently assigned addresses for documentation purposes with   the transient flag set to one, since the flag set to one means that   they are not permanently assigned.   For Source-Specific Multicast (SSM), it is less important which   multicast addresses are used, since a host/application joins a   channel identified by both source and group.  Any source addresses   used in SSM examples should be unicast addresses reserved for   documentation purposes.  The IPv6 unicast prefix reserved for   documentation purposes is 2001:DB8::/32, see [RFC3849].   Sometimes one wants to give examples where a specific type of address   is desired.  For example, for text about multicast scoping, one might   want the examples to use addresses that are to be used for   administrative scoping.  See below for guidance on how to construct   specific types of example addresses.Venaas, et al.                Informational                     [Page 4]

RFC 6676          Multicast Addresses for Documentation      August 20123.1.  Unicast Prefix-Based IPv6 Multicast Addresses   IPv6 multicast addresses can be derived from IPv6 unicast prefixes,   see [RFC3306].  For examples where this type of address is desired,   the addresses should be derived from the unicast addresses reserved   for documentation purposes.   The IPv6 unicast prefix reserved for documentation purposes is 2001:   DB8::/32, see [RFC3849].  This allows a wide range of different IPv6   multicast addresses.  Using just the base /32 prefix, one gets the   IPv6 multicast prefixes FF3X:20:2001:DB8::/64 -- one for each   available scope X.  One can also produce longer prefixes from this.   Just as an example, one can pick a /64 prefix 2001:DB8:DEAD:   BEEF::/64, which gives the multicast prefixes FF3X:40:2001:DB8:DEAD:   BEEF::/96 -- one for each available scope X.3.2.  Embedded-RP IPv6 Multicast Addresses   There is a type of IPv6 multicast address called an "Embedded-RP"   address, where the IPv6 address of a Rendezvous-Point (RP) is   embedded inside the multicast address, see [RFC3956].  For examples   where this type of address is desired, the addresses should be   derived from the unicast addresses reserved for documentation   purposes, see [RFC3849].   For documentation purposes, the RP address can be any address from   the range 2001:DB8::/32 that follows the constraints specified in   [RFC3956].  One example address could be 2001:DB8::1.  The   Embedded-RP multicast prefixes might then be FF7X:120:2001:DB8::/96.   Another example could be the RP address 2001:DB8:BEEF:FEED::7, which   gives the prefixes FF7X:740:2001:DB8:BEEF:FEED::/96.  See also the   examples in [RFC3956].4.  Security Considerations   The use of specific multicast addresses for documentation purposes   has no negative impact on security.5.  IANA Considerations   IANA has added a reference to this document for the IPv4 MCAST-TEST-   NET allocation so that all the different documentation multicast   assignments reference this document.   IANA has assigned a scope-relative IPv4 address for documentation   purposes.Venaas, et al.                Informational                     [Page 5]

RFC 6676          Multicast Addresses for Documentation      August 2012   IANA has assigned "variable-scope" IPv6 multicast addresses for   documentation purposes.  This is a /96 prefix.6.  Acknowledgments   The authors thank Roberta Maglione, Leonard Giuliano and Dave Thaler   for providing comments on this document.7.  Informative References   [RFC2365]  Meyer, D., "Administratively Scoped IP Multicast",BCP 23,RFC 2365, July 1998.   [RFC3180]  Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8",BCP 53,RFC 3180, September 2001.   [RFC3306]  Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6              Multicast Addresses",RFC 3306, August 2002.   [RFC3307]  Haberman, B., "Allocation Guidelines for IPv6 Multicast              Addresses",RFC 3307, August 2002.   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix              Reserved for Documentation",RFC 3849, July 2004.   [RFC3956]  Savola, P. and B. Haberman, "Embedding the Rendezvous              Point (RP) Address in an IPv6 Multicast Address",RFC 3956, November 2004.   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing              Architecture",RFC 4291, February 2006.   [RFC5398]  Huston, G., "Autonomous System (AS) Number Reservation for              Documentation Use",RFC 5398, December 2008.   [RFC5737]  Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks              Reserved for Documentation",RFC 5737, January 2010.   [RFC6034]  Thaler, D., "Unicast-Prefix-Based IPv4 Multicast              Addresses",RFC 6034, October 2010.Venaas, et al.                Informational                     [Page 6]

RFC 6676          Multicast Addresses for Documentation      August 2012Authors' Addresses   Stig Venaas   Cisco Systems   Tasman Drive   San Jose, CA  95134   USA   EMail: stig@cisco.com   Rishabh Parekh   Cisco Systems   Tasman Drive   San Jose, CA  95134   USA   EMail: riparekh@cisco.com   Gunter Van de Velde   Cisco Systems   De Kleetlaan 6a   Diegem  1831   Belgium   Phone: +32 476 476 022   EMail: gvandeve@cisco.com   Tim Chown   University of Southampton   Highfield   Southampton, Hampshire  SO17 1BJ   United Kingdom   EMail: tjc@ecs.soton.ac.uk   Marshall Eubanks   Iformata Communications   130 W. Second Street   Dayton, Ohio  45402   US   Phone: +1 703 501 4376   EMail: marshall.eubanks@iformata.com   URI:http://www.iformata.com/Venaas, et al.                Informational                     [Page 7]