Editing Multicast address (section)

==IPv6==

{{transcluded section|IPv6 address#IPv6-multicast-address-format}}

Multicast addresses in [[IPv6]] use the prefix {{IPaddr|ff00::|8}}.{{Ref RFC|4291}}
{{trim|{{#section:IPv6 address|IPv6-multicast-address-format}}}}

Based on the value of the flag bits, IPv6 multicast addresses can be '''Unicast-Prefix-based Multicast Addresses''',{{Ref RFC|3306}} '''Source-Specific Multicast Addresses''',{{Ref RFC|3306}} or '''Embedded RP IPv6 Multicast Addresses'''.{{Ref RFC|3956}} Each of these types of multicast addresses have their own format and follow specific rules.

Similar to a [[unicast]] address, the ''prefix'' of an IPv6 multicast address specifies its scope, however, the set of possible scopes for a multicast address is different. The 4-bit ''scope'' field (bits 12 to 15) is used to indicate where the address is valid and unique.

{| class="wikitable"
|+Multicast address scope
!IPv6 address<ref group=note>''x'' is a place holder indicating that the value of the ''flags'' field is unimportant in the current discussion.</ref>
!IPv4 equivalent{{Ref RFC|2365|rsection=8}}
!Scope{{Ref RFC|7346}}
!Purpose
|-
|{{mono|ffx0::/16, ffxf::/16}}
|
|Reserved
|-
|{{mono|ffx1::/16}}
|
|Interface-local
|Packets with this destination address may not be sent over any network link, but must remain within the current node; this is the multicast equivalent of the unicast [[loopback address]].
|-
|{{mono|ffx2::/16}}
|{{mono|224.0.0.0/24}}
|Link-local
|Packets with this destination address may not be routed anywhere.
|-
|{{mono|ffx3::/16}}
|{{mono|239.255.0.0/16}}
|Realm-Local scope{{Ref RFC|7346}}
|Local multicast particular to a network technology
|-
|{{mono|ffx4::/16}}
|
|Admin-local
|The smallest scope that must be administratively configured.
|-
|{{mono|ffx5::/16}}
|
|Site-local
|Restricted to the local physical network.
|-
|{{mono|ffx8::/16}}
|{{mono|239.192.0.0/14}}
|Organization-local
|Restricted to networks used by the organization administering the local network. (For example, these addresses might be used over [[VPN]]s; when packets for this group are routed over the public internet (where these addresses are not valid), they would have to be encapsulated in some other protocol.)
|-
|{{mono|ffxe::/16}}
|{{mono|224.0.1.0-238.255.255.255}}
|Global scope
|Eligible to be routed over the public internet.
|}

The service is identified in the ''group ID'' field. For example, if {{IPaddr|ff02::101}} refers to all [[Network Time Protocol]] (NTP) servers on the local network segment, then {{IPaddr|ff08::101}} refers to all NTP servers in an organization's networks. The ''group ID'' field may be [[IPv6 address#Multicast address format|further divided]] for special multicast address types.

===Notable IPv6 multicast addresses===
The following table is a list notable IPv6 multicast addresses that are registered with IANA.<ref>{{cite web |url=https://www.iana.org/assignments/ipv6-multicast-addresses/ipv6-multicast-addresses.xhtml |title=IPv6 Multicast Address Space Registry |publisher=[[Internet Assigned Numbers Authority]]}}</ref>
To be included in some of the below multicast groups a client must send a [[Multicast Listener Discovery]] (MLD), a component of [[ICMPv6]] suite, to join that group.{{Ref RFC|5110}} For example, to listen to {{IPaddr|ff02::1:ff28:9c5a}}, a client must send a MLD report to the router, containing the multicast address, to indicate that it wants to listen to that group.{{Ref RFC|2710}}

{| class="wikitable"
! Address
! Description
|-
| {{mono|ff02::1}}
| All nodes on the local network segment
|-
| {{mono|ff02::2}}
| All routers on the local network segment
|-
| {{mono|ff02::5}}
| [[OSPFv3]] All SPF routers
|-
| {{mono|ff02::6}}
| OSPFv3 All DR routers
|-
| {{mono|ff02::8}}
| [[IS-IS]] for IPv6 routers
|-
| {{mono|ff02::9}}
| [[Routing Information Protocol|RIP]] routers
|-
| {{mono|ff02::a}}
| [[EIGRP]] routers
|-
| {{mono|ff02::d}}
| [[Protocol Independent Multicast|PIM]] routers
|-
| {{mono|ff02::12}}
| [[Virtual Router Redundancy Protocol]] (VRRP) version 3
|-
| {{mono|ff02::16}}
| [[MLDv2]] reports{{Ref RFC|3810}}
|-
| {{mono|ff02::1:2}}
| All [[DHCPv6]] servers and relay agents on the local network segment{{Ref RFC|8415}}
|-
| {{mono|ff02::1:3}}
| All [[LLMNR]] hosts on the local network segment{{Ref RFC|4795}}
|-
| {{mono|ff05::1:3}}
| All DHCPv6 servers on the local network site{{Ref RFC|8415}}
|-
| {{mono|ff0x::c}}
| [[Simple Service Discovery Protocol#Protocol transport and addressing|Simple Service Discovery Protocol]]
|-
| {{mono|ff0x::fb}}
| [[Multicast DNS]]
|-
| {{mono|ff0x::101}}
| [[Network Time Protocol]]
|-
| {{mono|ff0x::108}}
| [[Network Information Service]]
|-
| {{mono|ff0x::181}}
| [[Precision Time Protocol]] (PTP) version 2 messages (Sync, Announce, etc.) except peer delay measurement
|-
| {{mono|ff02::6b}}
| [[Precision Time Protocol]] (PTP) version 2 peer delay measurement messages
|-
| {{mono|ff0x::114}}
| Used for experiments
|}