With the advent of more and more virtualization, and virtualized appliances, you may run across a situation where you need to assign a static MAC to a specific VM. Some virtual appliances use the MAC of the virtual NIC to figure out their licensing, so this would be a perfect example of needing to set a static MAC for the virtual machine. If/when the image moves inside the resource pool or is manually moved to a different host, if the MAC is not static, there is the specter of the VM losing the existing MAC and having a new one assigned. At this point the virtual appliance may lose its’ ability to use the license that was keyed to the MAC on the original load. The answer is to set a static MAC for that virtual machine. As a side note, you may also need to pay attention to doing this license process with only ONE NIC assigned to the VM.
For the VMware addicts:
For the Hyper-V folks:
For the Server 2012 Hyper-V users, the actual screens change a bit… here is a zippy screen shot.