initial mac address vs effective mac address

I have done some reading about Vmware Mac addresses but need some clarification:

initial mac address : is the Mac address of the virtual NIC of the Virtual machine
 effective mac address : is the Mac address of the Guest OS

OK, let 's say we have a physical PC and a Physical switch, The PC is connected to the the switch via the Network adapter.
the Network adapter will have it is burned Mac Address
on the PC (assuming it is Windows OS), if I run Getmac it will show the Mac address of the Network Adapter. I do not know of any reason to change the PC mac address from within the OS, or even if it let you change it.

So what would be the reason if changing effective Mac address on Vmware, which by default uses the initial Mac address ?

Thank you
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
You can spoof, or reburn a MAC Address into a physical adaptor if you know how!

The reason you may want to change the mac address on VMware from a VMware Vendor MAC Address to another vendor MAC Address, because of software licenses which are tied to a mac address, from a physical PC, you have done a P2V for!

Technically, this is called "spoofing"

Also to support Network Load Balancing you would have to change the MAC Addresses.

So you may not have a requirement at present, but it gives you the option, and flexibility to change them.
jskfanAuthor Commented:
confusion is Guest OS mac address and Virtual Nic Mac address

with  physical PC,  there is no OS Mac address and the Network Adapter Mac Address at the same time, there is only Network Adapter Mac Address
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Guest Mac OS - the OS which is generated in the OS.

Physical PC there is OS MAC Address = Physical MAC Address, unless you override it!

If you have the tools, you can generate a MAC Address and spoof and override the physical address.

Virtual NIC MAC Address which is the same as the Physical MAC Address in the real world! (burnt in on chip!

VMware makes it easier as the virtual mac address can be changed.
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jskfanAuthor Commented:
For instance in windows, you can run the command below to get Mac Address of the remote computer.

C:\>getmac /S  /u administrator /p adminpassword
Physical Address    Transport Name
=================== ==========================================================
22-15-25-9C-3A-29   Media disconnected
34-11-45-7A-9C-48   \Device\Tcpip_{678DD7BB-675D-4E4C-E0AE-A261490EBE8C}

Now the Mac addresses shown above are they OS Mac addresses or of the existing Network connections ?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
They are the mac addresses which are currently sending traffic from the nic. So OS Mac Addresses,

I have Linux machines, where the OS has overridden the MAC Address of the real network card, these are OS MAC Addresses.

e.g. spoofed mac addresses.
jskfanAuthor Commented:
OK so the one I displayed above with Getmac cooomand is different than the physical Network Adapter of the computer ?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
it could be! the majority of the time, I would expect it to be, unless it's been spoofed!

that is the mac address currently "talking on the wire", as reported by your OS, and the OS which is currently installed on that target computer.

BUT, it may not be the MAC Address burned in on the chip on the network interface!

the only way to check that, is physically inspect it, or boot with another OS.

Have a read on the topic of spoofing...

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jskfanAuthor Commented:
Thank you
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