Q:

Do ESXi vSwitches have their own mac address?

I'm in the process of trying to decommission a few subnets which are believed to be no longer in use.  When I query the mac address table on the physical switch for the vlans associated with these subnets, I see quite a few mac addresses beginning with 00:50:56 (VMware) which I am not able to correlate to any specific VM.  Instead it appears that these mac addresses may be used by the vSwitch itself.  Do ESXi (5.5) vSwitches themselves have their own mac address, separate and in addition to the mac addresses for the VMs?  If so, what circumstances require a vSwitch to send frames from this mac address?  Does this apply equally to Standard and Distributed switches?

A:

Do ESXi (5.5) vSwitches themselves have their own mac address

Yes.

What circumstances require a vSwitch to send frames from this mac
  address?

Beacon probing, RARP, a few things.

Does this apply equally to Standard and Distributed switches

Yes.

