MAC address will only generate when you will add or remove NIC to VM or you Manually change MAC address, I don't see why MAC address would change as it is only attached to NIC not to VM!!
However it will good to hear from experts
I know at least it will change when you generate a new UUID and I know with previous versions a cold clone would also regenerate a MAC. I think clones also regenerate MAC, so would like to see if there is a definitive list for each version of ESX.
yes, anytime a VM is booted, the host (and VC if it's connected to one) checks other running VM's to see if the MAC is already being used and generates a new MAC for the booting VM.
As others have indicated a MAC address is generated every time a VM is powered on - the MAC address is generated using the UUID of the ESX and the directory location of the V<s configuration file - you can also set the MAC address in the configuration file and a MAC will never get generated for this VM -
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Major two things will involve to generate or change the MAC address
1.When cloning the machine(if MAC conflict)
2.Converting V2V or P2V
We can generate the new MAC and avoid the conflicts.
I hope it will help you.
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Read KB 219, it contains a lot of information regarding the MAC address handling in ESX.
VCP 3 & 4
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