Hi,
Have gone through this article?
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=219
I don't think you can use a non vmware mac address in ESX, but workstation you can.
VMware ESX Server virtual machines do not support arbitrary MAC addresses, hence the above format must be used. As long as you choose a hex value that is unique among your hard-coded addresses, conflicts between the automatically assigned MAC addresses and the manually assigned ones should never occur.
