RFC 6676

Multicast Addresses for Documentation

📅 published August 2012, from ietf

Multicast Addresses for Documentation (RFC 6676) 🎀

okay bestie, RFC 6676 is an Informational doc from the IETF 💅 and it's all about which multicast addresses you should grab for examples, so nothing real gets accidentally hijacked 🦋

Here's the title block tea ☕

Number and title: RFC 6676, Multicast Addresses for Documentation 💖
Authors: S. Venaas, R. Parekh, G. Van de Velde (Cisco Systems), T. Chown (University of Southampton), and M. Eubanks (Iformata Communications) 🫶
Category: Informational
ISSN: 2070-1721
Date: August 2012
Obsoletes and updates: the header doesn't list anything it obsoletes or updates ✨

Abstract

so the gist is this: the doc talks about which multicast addresses should be used for documentation and reserves some of them for that job 🌸 Some multicast addresses are derived from AS numbers or unicast addresses, and the doc explains how you can use those for documentation too 🧚

Status of This Memo

this one is not an Internet Standards Track spec, it's published just for info 📖

it's still an IETF product that represents the IETF community's consensus 🫶 It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). Not every IESG-approved doc is up for any level of Internet Standard, so check Section 2 of RFC 5741 if you're curious 🤓

the status, errata, and feedback info lives at http://www.rfc-editor.org/info/rfc6676 🔗

Copyright Notice

this doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) as they were on the publication date. read those carefully, they spell out your rights and restrictions 📜 Code Components pulled out of this doc must include the Simplified BSD License text described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as the Simplified BSD License says 🌈

   1. Introduction ....................................................2
   2. IPv4 Multicast Documentation Addresses ..........................3
      2.1. Administratively Scoped IPv4 Multicast Addresses ...........3
      2.2. GLOP Multicast Addresses ...................................3
      2.3. Unicast Prefix-Based IPv4 Multicast Addresses ..............4
   3. IPv6 Multicast Documentation Addresses ..........................4
      3.1. Unicast Prefix-Based IPv6 Multicast Addresses ..............5
      3.2. Embedded-RP IPv6 Multicast Addresses .......................5
   4. Security Considerations .........................................5
   5. IANA Considerations .............................................5
   6. Acknowledgments .................................................6
   7. Informative References ..........................................6

1. Introduction ✨

okay so docs, IETF stuff, etc. love putting IP multicast addresses in examples 🍓 If you're writing an example that needs a general-purpose multicast address, you should use one that will never be assigned or actually in use. The risk is that an address from an example gets used by accident, so it's important that the same addresses aren't used by other multicast apps or services 🙈 It may also be helpful to filter those addresses out of multicast signalling, and to filter out multicast data sent to them 🛡️

for unicast, there are IPv4 and IPv6 addresses reserved for exactly this, see [RFC5737] and [RFC3849] 💖 This doc reserves multicast addresses for the same purpose.

some multicast addresses are derived from AS numbers or unicast addresses too 🦋 If you want examples with those, derive them from the AS numbers and unicast addresses reserved for documentation. The doc talks about how to do that as well 🧚

2. IPv4 Multicast Documentation Addresses 🌸

for Any-Source Multicast (ASM), the IPv4 multicast addresses reserved for documentation are 233.252.0.0 - 233.252.0.255 (233.252.0.0/24) 💅

for Source-Specific Multicast (SSM), which addresses you pick matters less, because a host or app joins a channel identified by both source and group 👑 Any source addresses in SSM examples should be unicast addresses reserved for documentation. There are three unicast ranges for that in [RFC5737]: 192.0.2.0/24, 198.51.100.0/24, and 203.0.113.0/24 🫶

sometimes you want an example with a specific type of address. Say you're writing about multicast scoping and want addresses used for administrative scoping. Below is guidance on building those specific 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 aren't 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 it represents an IPv4 address. For documentation, the integer offset is 10, which gives you one multicast address per scope 🌈

for example, in the Local Scope 239.255.0.0/16, the multicast address for documentation 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 ✨ If you want GLOP addresses in examples, derive them from the AS numbers reserved for documentation use.

the 16-bit AS numbers reserved for documentation in [RFC5398] are 64496 - 64511. Using [RFC3180], that gives you 16 /24 multicast prefixes for documentation. The first is 233.251.240.0/24, and the last 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 that need this type of address, derive them from the unicast addresses reserved for documentation, see [RFC5737].

again, the three unicast ranges reserved for documentation in [RFC5737] are 192.0.2.0/24, 198.51.100.0/24, and 203.0.113.0/24. Using [RFC6034], that leaves you 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 reserved for documentation are FF0X::DB8:0:0/96 💅 It's a /96 prefix so it can be used with group IDs, following the allocation guidelines in [RFC3307] 🫶 These addresses also have the transient flag, or "T-flag" as defined in [RFC4291], set to zero, because they're permanently assigned. There can be no permanently assigned documentation addresses with the transient flag set to one, since a flag of one means they aren't permanently assigned 🙅‍♀️

for Source-Specific Multicast (SSM), the address choice matters less again, since a host or app joins a channel identified by both source and group 👑 Any source addresses in SSM examples should be unicast addresses reserved for documentation. The IPv6 unicast prefix reserved for documentation is 2001:DB8::/32, see [RFC3849] 🌸

sometimes you want an example with a specific type of address, like addresses used for administrative scoping in multicast scoping text. Below is guidance on building those specific example addresses 🎀

3.1. Unicast Prefix-Based IPv6 Multicast Addresses

IPv6 multicast addresses can be derived from IPv6 unicast prefixes, see [RFC3306] 🦋 For examples that need this type of address, derive them from the unicast addresses reserved for documentation.

the IPv6 unicast prefix reserved for documentation is 2001:DB8::/32, see [RFC3849]. That allows a wide range of IPv6 multicast addresses 🌈 Using just the base /32 prefix, you get the IPv6 multicast prefixes FF3X:20:2001:DB8::/64, one for each available scope X ✨ You can also make longer prefixes from it. As just an example, you can pick the /64 prefix 2001:DB8:DEAD:BEEF::/64, which gives the multicast prefixes FF3X:40:2001:DB8:DEAD:BEEF::/96, again one for each available scope X 💜

3.2. Embedded-RP IPv6 Multicast Addresses

there's 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 that need this type of address, derive them from the unicast addresses reserved for documentation, see [RFC3849].

for documentation, the RP address can be any address from the range 2001:DB8::/32 that follows the constraints in [RFC3956] 💅 One example RP address is 2001:DB8::1, and the Embedded-RP multicast prefixes could then be FF7X:120:2001:DB8::/96. Another example is 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] 🦋

next up: security, IANA, and the rest of the references 🎀✨

7. Informative References ✨

okay bestie, this is the reading list 📚 every title, number, and date is exactly as the original has it, so you can go find the good stuff yourself 🦋

[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.

Authors' Addresses 💌

the people behind this doc, with their contact details exactly as listed 🫶

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/

that's the whole doc, bestie 💖✨ five authors, zero chill, and one very iconic spec 👑

📦 where this page comes from

ietf: rfc6676 2012-08
💖 girlified by claude-haiku-5-5 on 2026-10-17: a language model's rewrite of the original, under its terms