mulitcast mac-address

[pccthailand]

Hi

Could anyone explain me about multicast address on switch such as 0100.0ccc.cccc / 0100.0ccc.cccd or 0100.0cdd.dddd . How switch use it ?

Thanks

[leonvd79]

Hello,

The multicast addresses belong to various services, such as Cisco Discovery Protocol, Spanning Tree Protocol and Virtual Trunking Protocol.

CDP and VTP multicast address equals to 0100.0ccc.cccc

BPDU multicast address equals to 0100.0ccc.cccd

CGMP multicast address equals to 0100.0cdd.dddd

HTH

--Leon

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[Roberto Salazar]

These addresses are used for control packet such CDP/DTP/VTP/Pagp, STP and CGMP.

0100.0ccc.cccc - CDP/DTP/VTP/Pagp/UDLD, Depending on SNAP protocol type.

0100.0ccc.cccd - STP >> BPDUs generated by a Cisco Catalyst switch on 802.1q trunks are destined to the MAC address 0180.C200.0000 only for VLAN 1: BPDUs for other vlans have a destination MAC address of 0100.0CCC.CCCD. This address is a multicast address and it is Cisco proprietary.

The 802.1d standard mandates the use of the Mac address 0180.C200.0000. Cisco uses 0100.0CCC.CCCD to achieve tunneling of Vlans other than vlan 1 on a MST cloud.

0100.0cdd.dddd - CGMP >> Router sends CGMP multicast packets to the switches at a well known multicast MAC address: ? 0100.0cdd.dddd

Switches send and listen for packets destined to these mac-addresses.

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