Editing Multicast address (section)

==IPv4==<!--[[IPv4 multicast address]] redirects here-->
[[IPv4]] multicast addresses are defined by the [[most-significant bit]] pattern of ''1110''. This originates from the [[classful network]] design of the early Internet when this group of addresses was designated as ''Class D''. The [[CIDR notation]] for this group is {{IPaddr|224.0.0.0|4}}.<ref>[https://www.ge.com/digital/documentation/cimplicity/version10/oxy_ex-2/advanced_features/topics/g_cimplicity_advanced_features_multicast_ip_addr.html MULTICAST_IP_ADDR]. [[General Electric]] Digital Solutions. [[CIMPLICITY]] 10.0. <q>In network prefix or Classless Inter-Domain Routing ( CIDR) notation, IP multicast addresses are summarized as 224.0.0.0/4.</q></ref> The group includes the addresses from {{IPaddr|224.0.0.0}} to {{IPaddr|239.255.255.255}}.

The address range is divided into blocks each assigned a specific purpose or behavior.{{Ref RFC|5771}}
{| class="wikitable"
|-
!IP multicast address range
!Description
!Routable
|-
|224.0.0.0 to 224.0.0.255
|Local subnetwork<ref name="Cisco Multicast">{{citation |url=https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/15-2_2_e/multicast/configuration_guide/b_mc_1522e_3750x_3560x_cg/b_mc_3750x_3560x_chapter_01.html |title=IP Multicast Routing Configuration Guide |publisher=[[Cisco]] |access-date=2021-01-13}}</ref>
|{{No}}
|-
|224.0.1.0 to 224.0.1.255
|Internetwork control
|{{Yes}}
|-
|224.0.2.0 to 224.0.255.255
|AD-HOC block 1<ref>[https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml#multicast-addresses-3 AD-HOC Block 1]</ref>
|{{Yes}}
|-
|224.1.0.0 to 224.1.255.255
|Reserved{{Ref RFC|5771|rsection=3}}<ref name="IANA IP"/>
|
|-
|224.2.0.0 to 224.2.255.255
|SDP/SAP block<ref>[https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml#multicast-addresses-5 SDP/SAP Block]</ref>
|{{Yes}}
|-
|224.3.0.0 to 224.4.255.255
|AD-HOC block 2<ref>[https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml#multicast-addresses-6 AD-HOC Block 2]</ref>
|{{Yes}}
|-
|224.5.0.0 to 224.255.255.255
|Reserved{{Ref RFC|5771|rsection=3}}<ref name="IANA IP"/>
|
|-
|225.0.0.0 to 231.255.255.255
|Reserved{{Ref RFC|5771|rsection=3}}<ref name="IANA IP"/>
|
|-
|232.0.0.0 to 232.255.255.255
|Source-specific multicast<ref name="Cisco Multicast"/>
|{{Yes}}
|-
|233.0.0.0 to 233.251.255.255
|GLOP addressing<ref name=fall2011tcp>{{cite book |title=TCP/IP Illustrated |author=Fall, K.R. and Stevens, W.R. |volume=1 |isbn=9780321336316 |url=https://books.google.com/books?id=X-l9NX3iemAC |date=2011 |publisher=Addison-Wesley |page=55}}</ref>
|{{Yes}}
|-
|233.252.0.0 to 233.255.255.255
|AD-HOC block 3<ref>[https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml#multicast-addresses-11 AD-HOC Block 3]</ref>
|{{Yes}}
|-
|234.0.0.0 to 234.255.255.255
|Unicast-prefix-based<ref>[https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml#unicast-prefix-based Unicast-Prefix-based IPv4 Multicast Addresses]</ref>
|{{Yes}}
|-
|235.0.0.0 to 238.255.255.255
|Reserved{{Ref RFC|5771|rsection=3}}<ref name="IANA IP"/>
|
|-
|239.0.0.0 to 239.255.255.255
|Administratively scoped<ref name="Cisco Multicast"/>
|{{Yes}}
|}

;Local subnetwork
:Addresses in the range of {{IPaddr|224.0.0.0}} to {{IPaddr|224.0.0.255}} are individually assigned by IANA and designated for multicasting on the local [[subnetwork]] only. For example, the [[Routing Information Protocol]] (RIPv2) uses {{IPaddr|224.0.0.9}}, [[Open Shortest Path First]] (OSPF) uses {{IPaddr|224.0.0.5}} and {{IPaddr|224.0.0.6}}, and [[Multicast DNS]] uses {{IPaddr|224.0.0.251}}. Routers must not forward these messages outside the subnet from which they originate.

;Internetwork control block
:Addresses in the range {{IPaddr|224.0.1.0}} to {{IPaddr|224.0.1.255}} are individually assigned by IANA and designated as the ''internetwork control block''. This block of addresses is used for traffic that must be routed through the public Internet, such as for applications of the [[Network Time Protocol]] using {{IPaddr|224.0.1.1}}.

;AD-HOC block <!-- Note:  The hyphenated spelling is in the RFC.  -->
:Addresses in three separate blocks are not individually assigned by IANA. These addresses are globally routed and are used for applications that don't fit either of the previously described purposes.{{Ref RFC|5771|rsection= 6}}

;SDP/SAP block
:Addresses in the reserved {{IPaddr|224.2.0.0|16}} range are not individually assigned by IANA. Fallen out of use {{Ref RFC|8866|rsection=10}} for security considerations, experimental [[Session Announcement Protocol]] {{Ref RFC|2974}} was the primary means of supplying addresses through [[Session Description Protocol]], which now is mostly used in the establishment of private sessions.

;Source-specific multicast
:The {{IPaddr|232.0.0.0|8}} (IPv4) and {{IPaddr|FF3x::|32}} (IPv6) blocks are reserved for use by [[source-specific multicast]].

;GLOP<ref>{{Cite book|title=Deploying Next Generation Multicast-Enabled Applications - Label Switched Multicast for MPLS, VPN, VPLS, and Wholesale Ethernet|author1-last=Joseph|author1-first=Vinod|author2-last=Mugulu|author2-first=Srinivas|publisher=Morgan Kaufmann/Elsevier|year=2011|isbn=978-0-12-384923-6|page=7|quote="Lacking anything better to call it, one of the authors [of RFC2770], David Meyer, simply began refer to this as "GLOP" addressing and the name stuck."}}</ref>
:The {{IPaddr|233.0.0.0|8}} range was originally assigned as an experimental, public statically-assigned multicast address space for publishers and Internet service providers that wished to source content on the Internet.{{Ref RFC|2770}} The allocation method is termed GLOP addressing and provides implementers a block of 255 addresses that is determined by their 16-bit [[autonomous system number]] (ASN) allocation. In a nutshell, the middle two [[octet (computing)|octet]]s of this block are formed from assigned ASNs, giving any operator assigned an ASN 256 globally unique multicast group addresses.<ref>{{cite web |url=http://www.multicasttech.com/faq/ |archive-url=https://web.archive.org/web/20110516204230/http://www.multicasttech.com/faq/ |title=Frequently Asked Questions (FAQ) File for Multicasting |publisher=Multicast Tech |archive-date=2011-05-16}}</ref> The method is not applicable to the newer 32-bit ASNs. In {{date|September 2001}}, the [[IETF]] envisioned a broader use of the range for many-to-many multicast applications.{{Ref RFC|3180}} Unfortunately, with only 256 multicast addresses available to each autonomous system, GLOP is not adequate for large-scale broadcasters.{{citation needed|date=January 2019}}

;Unicast-prefix-based
:The {{IPaddr|234.0.0.0|8}} range is assigned as a range of global IPv4 multicast address space provided to each organization that has {{IPaddr||24}} or larger globally routed unicast address space allocated; one multicast address is reserved per {{IPaddr||24}} of unicast space.{{Ref RFC|6034}} A resulting advantage over GLOP is that the unicast-prefix mechanism resembles the unicast-prefix capabilities of IPv6.{{Ref RFC|3306}}

;Administratively scoped
:The {{IPaddr|239.0.0.0|8}} range is assigned for private use within an organization.{{Ref RFC|2365}} Packets destined to administratively scoped IPv4 multicast addresses do not cross administratively defined organizational boundaries, and administratively scoped IPv4 multicast addresses are locally assigned and do not have to be globally unique.  The {{IPaddr|239.0.0.0|8}} range may be structured to be loosely similar to the scoped IPv6 multicast address.{{Ref RFC|4291}}

;Ethernet-specific
:In support of link-local multicasts which do not use IGMP, any IPv4 multicast address that falls within the {{IPaddr|*.0.0.0|24}} and {{IPaddr|*.128.0.0|24}} ranges will be broadcast to all ports on many Ethernet switches, even if [[IGMP snooping]] is enabled, so addresses within these ranges should be avoided on Ethernet networks where the functionality of IGMP snooping is desired.<ref>{{cite web |url=https://www.cisco.com/c/dam/en/us/support/docs/ip/ip-multicast/ipmlt_wp.pdf#page=7 |page=7 |title=Guidelines for Enterprise IP Multicast Address Allocation |publisher=[[Cisco]] |access-date=2023-01-14 |quote=most Layer 2 switches flood all multicast traffic that falls within the MAC address range of 0x0100.5E00.00xx [...] to all ports on the switch even if IGMP Snooping is enabled. [...] There are several multicast group ranges besides the 224.0.0.0/24 that will map to the 0x0100.5E00.00xx MAC address range and hence also will be flooded by most Layer 2 switches.}}</ref>{{dubious|Ethernet-specific|date=January 2023}}

===Notable IPv4 multicast addresses===
The following table is a list of notable well-known IPv4 addresses that are reserved for [[IP multicast]]ing and that are registered with the [[Internet Assigned Numbers Authority]] (IANA).<ref name="IANA IP"/>

{| class="wikitable"
|-
!IP multicast address
!Description
!Routable
|-
|224.0.0.0
|Base address (reserved)
|{{No}}
|-
|224.0.0.1
|The ''All Hosts'' multicast group addresses all hosts on the same network segment.
|{{No}}
|-
|224.0.0.2
|The ''All Routers'' multicast group addresses all routers on the same network segment.
|{{No}}
|-
|224.0.0.4
|This address is used in the [[Distance Vector Multicast Routing Protocol]] (DVMRP) to address multicast routers.
|{{No}}
|-
|224.0.0.5
|The [[Open Shortest Path First]] (OSPF) ''All OSPF Routers'' address is used to send Hello packets to all OSPF routers on a network segment.
|{{No}}
|-
|224.0.0.6
|The OSPF ''All Designated Routers'' (DR) address is used to send OSPF routing information to designated routers on a network segment.
|{{No}}
|-
|224.0.0.9
|The [[Routing Information Protocol]] (RIP) version 2 group address is used to send routing information to all RIP2-aware routers on a network segment.
|{{No}}
|-
|224.0.0.10
|The [[Enhanced Interior Gateway Routing Protocol]] (EIGRP) group address is used to send routing information to all EIGRP routers on a network segment.
|{{No}}
|-
|224.0.0.13
|[[Protocol Independent Multicast]] (PIM) Version 2
|{{No}}
|-
|224.0.0.18
|[[Virtual Router Redundancy Protocol]] (VRRP)
|{{No}}
|-
|224.0.0.19–21
|[[IS-IS]] over IP
|{{No}}
|-
|224.0.0.22
|[[Internet Group Management Protocol]] (IGMP) version 3{{Ref RFC|3376|rsection=4.2.14}}
|{{No}}
|-
|224.0.0.102
|[[Hot Standby Router Protocol]] version 2 (HSRPv2) / [[Gateway Load Balancing Protocol]] (GLBP)
|{{No}}
|-
|224.0.0.107
| [[Precision Time Protocol]] (PTP) version 2 peer delay measurement messaging
|{{No}}
|-
|224.0.0.251
|[[Multicast DNS]] (mDNS) address
|{{No}}
|-
|224.0.0.252
|[[Link-local Multicast Name Resolution]] (LLMNR) address
|{{No}}
|-
|224.0.0.253
|[[Teredo tunneling]] client discovery address{{Ref RFC|4380|rsection=2.17}}
|{{No}}
|-
|224.0.1.1
|[[Network Time Protocol]] clients listen on this address for protocol messages when operating in multicast mode.
|{{Yes}}
|-
|224.0.1.22
|[[Service Location Protocol]] version 1 general
|{{Yes}}
|-
|224.0.1.35
|[[Service Location Protocol]] version 1 directory agent
|{{Yes}}
|-
|224.0.1.39
|The Cisco multicast router ''AUTO-RP-ANNOUNCE'' address is used by RP mapping agents to listen for candidate announcements.
|{{Yes}}
|-
|224.0.1.40
|The Cisco multicast router ''AUTO-RP-DISCOVERY'' address is the destination address for messages from the RP mapping agent to discover candidates.
|{{Yes}}
|-
|224.0.1.41
|[[H.323 Gatekeeper]] discovery address
|{{Yes}}
|-
|224.0.1.129–132
|[[Precision Time Protocol]] (PTP) version 1 messages (Sync, Announce, etc.) except peer delay measurement
|{{Yes}}
|-
|224.0.1.129
|[[Precision Time Protocol]] (PTP) version 2 messages (Sync, Announce, etc.) except peer delay measurement
|{{Yes}}
|-
|224.0.23.12
|[[KNX#IP|KNXnet/IP]] discovery<ref>{{Cite web |title=IPv4 Multicast Address Space Registry |url=https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml |access-date=2024-06-30 |website=www.iana.org}}</ref>
|{{Yes}}
|-
|239.255.255.250
|[[Simple Service Discovery Protocol]] address
|{{Yes}}
|-
|239.255.255.253
|[[Service Location Protocol]] version 2 address
|{{Yes}}
|}