Editing Multicast address (section)

==Ethernet==
Ethernet frames with a value of 1 in the least-significant bit of the first octet<ref group=note>On Ethernet, the least-significant bit of an octet is the first to be transmitted. A multicast is indicated by the first transmitted bit of the destination address being 1.</ref> of the destination [[MAC address]] are treated as multicast frames and are flooded to all points on the network. While frames with ones in all bits of the destination address ({{macaddr|FF-FF-FF-FF-FF-FF}}) are sometimes referred to as [[Broadcasting (networking)|broadcasts]], Ethernet generally does not distinguish between multicast and broadcast frames. Modern Ethernet controllers filter received packets to reduce CPU load, by looking up the hash of a multicast destination address in a table, initialized by software, which controls whether a multicast packet is dropped or fully received.

The IEEE has allocated the address block {{macaddr|01-80-C2-00-00-00}} to {{macaddr|01-80-C2-FF-FF-FF}} for group addresses for use by standard protocols. Of these, the MAC group addresses in the range of {{macaddr|01-80-C2-00-00-00}} to {{macaddr|01-80-C2-00-00-0F}} are not forwarded by [[802.1D]]-conformant [[MAC bridge]]s.<ref>{{cite web |author=IEEE |url=http://standards.ieee.org/develop/regauth/tut/macgrp.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://standards.ieee.org/develop/regauth/tut/macgrp.pdf |archive-date=2022-10-09 |url-status=dead |title=Standard Group MAC Address: A Tutorial Guide |publisher=IEEE Standards Association |pages=2–3}}</ref>

{| class="wikitable" <!--note xx-xx-xx-xx-xx-xx is preferred IEEE notation for MAC addresses. See [[MAC_address#Notational_conventions]]. Please use this format in this section.-->
|-
|+Some well known [[Ethernet]] multicast addresses<ref>{{cite web |author=Patton, Michael A.|display-authors=etal|url=http://www.cavebear.com/archive/cavebear/Ethernet/multicast.html |title=Multicast (including Broadcast) Addresses|work=cavebear.com |publisher=[[Karl Auerbach]]}}</ref>
!Block
!Ethernet multicast address
![[Ethertype]]
!Usage
|-
|rowspan="15"|
01-80-C2<ref>{{cite web |title=Standard Group MAC Address - Public Listing |url=https://standards.ieee.org/products-programs/regauth/grpmac/public/ |publisher=IEEE-SA |access-date=30 November 2022}}</ref><br/>
<small>[[IEEE]] (802 group)</small>
|rowspan="3"|
{{macaddr|01-80-C2-00-00-00}}
|colspan="2" style="background-color:#def"| Local LAN Segment, stopping at STP-capable switches
|-
|[[Subnetwork Access Protocol|SNAP]] (length)
|[[Spanning Tree Protocol]] (for bridges) [[IEEE 802.1D]]
|-
|0x88CC
|[[Link Layer Discovery Protocol]] (additional)
<!-------------- end -00 ---------------->
|-
|{{macaddr|01-80-C2-00-00-01}}
|0x8808
|[[Ethernet flow control]] (pause frame) [[IEEE 802.3x]]
|-
|{{macaddr|01-80-C2-00-00-02}}
|0x8809
|"Slow protocols" including [[Operations, administration and management|Ethernet OAM Protocol]] ([[IEEE 802.3ah]]) and [[Link Aggregation Control Protocol]] (LACP)
|-
|rowspan="3"|
{{macaddr|01-80-C2-00-00-03}}
|colspan="2" style="background-color:#def"| Local LAN Segment until next multi-port ("non-TPMR") switch
|-
|0x888E
|Port authentication ([[IEEE 802.1X]] EAPOL)
|-
|0x88CC
|Link Layer Discovery Protocol (additional)
|-
|{{macaddr|01-80-C2-00-00-08}}
|SNAP (length)
|Spanning Tree Protocol (for provider bridges) [[IEEE 802.1ad]]
|-
|{{macaddr|01-80-C2-00-00-0D}}
|0x88F5
|Multiple VLAN Registration Protocol (for provider bridges) [[IEEE 802.1ad]]
|-
|rowspan="3"|{{macaddr|01-80-C2-00-00-0E}}
|colspan="2" style="background-color:#def"| Local LAN Link, never crosses another device
|-
|0x88CC
|[[Link Layer Discovery Protocol]] (primary)
|-
|0x88F7
|[[Precision Time Protocol]] (PTP) version 2 over Ethernet (802.1AS)
|-
|{{macaddr|01-80-C2-00-00-21}}
|0x88F5
|[[GARP VLAN Registration Protocol]] (also known as [[IEEE 802.1Q]] GVRP)<br/>
Multiple VLAN Registration Protocol (MVRP)
|-
|{{macaddr|01-80-C2-00-00-30}} through<br/>{{macaddr|01-80-C2-00-00-3F}}
|0x8902
|Ethernet CFM Protocol [[IEEE 802.1ag]] 
|-
|rowspan="1"|
01-1B-19<br/>
<small>[[IEEE]] (TC9)</small>
|{{macaddr|01-1B-19-00-00-00}}
|0x88F7
|[[Precision Time Protocol]] (PTP) version 2 over Ethernet (native layer-2)<br/>for electing the Grandmaster clock and advanced applications, otherwise {{MACaddr|01-80-C2-00-00-0E}}
|-
|rowspan="1"|
01-00-5E<ref>{{cite web |title=IANA Multicast 48-bit MAC Addresses |url=https://www.iana.org/assignments/ethernet-numbers/ethernet-numbers.xhtml#ethernet-numbers-3 |publisher=IANA |access-date=31 January 2021}}</ref><br/>
<small>[[ICANN]]/[[IANA]]</small>
|{{macaddr|01-00-5E-00-00-00}} through<br/>{{macaddr|01-00-5E-7F-FF-FF}}
|0x0800
|IPv4 Multicast:{{Ref RFC|1112}} Insert the low 23 bits of the multicast IPv4 address into the Ethernet address{{Ref RFC|7042|rsection=2.1.1}}
|-
|rowspan="1"|
33-33-xx<br/>
<small>''locally administered''</small>
|{{MACaddr|33-33-00-00-00-00}} through<br/>{{MACaddr|33-33-FF-FF-FF-FF}}
|0x86DD
|IPv6 multicast:{{Ref RFC|2464}} The low 32 bits an Ethernet address for IPv6 multicast traffic are the low 32 bits of the multicast IPv6 address used.{{Ref RFC|7042|rsection=2.3.1}} For example, IPv6 multicast traffic using the address {{IPaddr|ff02::d}} uses the MAC address {{MACaddr|33-33-00-00-00-0d}}, and traffic to {{IPaddr|ff05::1:3}} goes to the MAC address {{MACaddr|33-33-00-01-00-03}}.
|-
|rowspan="3"|
01-0C-CD<br/>
<small>[[IEC]]</small>
|{{macaddr|01-0C-CD-01-00-00}} through<br/>{{macaddr|01-0C-CD-01-01-FF}}
|0x88B8
|[[IEC 61850]]-8-1 GOOSE Type 1/1A
|-
|{{macaddr|01-0C-CD-02-00-00}} through<br/>{{macaddr|01-0C-CD-02-01-FF}}
|0x88B9
|GSSE (IEC 61850 8-1)
|-
|{{macaddr|01-0C-CD-04-00-00}} through<br/>{{macaddr|01-0C-CD-04-01-FF}}
|0x88BA
|Multicast sampled values (IEC 61850 8-1)
|-
|rowspan="2"|
01-00-0C<br/>
<small>[[Cisco Systems]]</small>
|{{macaddr|01-00-0C-CC-CC-CC}}
|SNAP (length)
|[[Cisco Discovery Protocol]] (CDP), [[VLAN Trunking Protocol]] (VTP), [[Unidirectional Link Detection]] (UDLD)
|-
|{{macaddr|01-00-0C-CC-CC-CD}}
|SNAP (length)
|Cisco Shared Spanning Tree Protocol Address{{citation needed|date=April 2020}}
|}