LabView uses the "primary" MAC address to identify a machine. If the MAC address changes, LabView assumes the software no longer has a valid activation and displays the following:
Like many developers, I have to use a VPN to connect to a corporate network. My VPN client creates a pseudo-interface with a (random?) MAC address each time I connect. LabView inspects this MAC address and decides I've installed LabView on a new machine, forcing me to go through the activation process again. I have to activate LabView about every 10 days. I have contacted support about this, and they have given me various work-arounds such as non-expiring activation codes (which required manually entering 10 activation codes, one per product, and only work until the next LabView service pack), or tying activation to the Disk Volume ID, which frankly I did not bother trying since the "eligibility on a case by case basis" did not mesh with the reality that every point release of LabView requires re-activation.
Now, I don't want to make too much of this. I've never had the activation fail, and it is pretty fast, so it's really not a big deal, but it is kind of silly to identify a machine based on a mutable property. Heck, on linux it's trivial to change the MAC address to anything you want! (I tried this with my VPN client, but it had none of it.)
I suggest the activation process something more stable, like the CPUID on Intel processors or, barring that, restricting the MAC address search to physical interfaces.