two ports on the switch register the same MAC address

[Tod Larson]

I am investigating implementing Microsoft Load Balacing.  This seems to be the best documentation on this topic.

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a0080a07203.shtml#mm

However,

It recommendes implementing this command on my switch.

mac-address-table static 0300.5e11.1111 vlan 200 interface fa2/3 fa2/4

This command appears to be populating the mac table with the same MAC on two ports (fa2/3 and fa2/4).

How does that work?  I thought a MAC can only be on a single port.  What is going on behind the scenes here?

Thank you.

[Jon Marshall · Accepted solution]

Tod

A unicast mac address should be seen on only one port within the same vlan but the mac-address in that command is a multicast mac-address and more than one port can be a member of a multicast group.

Jon