The question came up during a #vBrownBag: “How do you disable that annoying little popup for promiscuous mode”. If you have worked with Autolab, you will have seen it too. About 8 times each Autolab build (4 for each nested esxi host).
To bypass it in Fusion 6, there are two methods:
Disabling Promiscuous Mode Authentication – Fusion 6 Pro
There is a handy Networking dialogue to take care of it (Image thanks to @nickmarshall9)
Disabling Promiscuous Mode Authentication on Fusion 6 Standard
This one is a bit more complicated as the network editor is seemingly only available in the pro edition. To disable the prompting for promiscuous authentication, create the following file:
sudo touch "/Library/Preferences/VMware Fusion/promiscAuthorized"
Then restart Fusion.
Thanks to: @toonces77, @nickmarshall9, and @mikefoley for helping with the details.