As mentioned previously, I’ve been using Sun’s VirtualBox to do some software evaluations requiring multiple servers. Until very recently (like an hour ago), I was using my laptop and one VirtualBox vm.
Then, I decided to try a second vm. I cloned the vm, generated a new mac address for the new vm’s network adapter, and started the vm. No network. Just the loopback interface. Huh?
I tried everything that I could think of, and then finally resorted to Google. There, buried in the haystack of useless answers was this gem.
So, for my own reference (and yours), the answer, at least for an Ubuntu guest, is to edit /etc/udev/rules.d/70-persistent-net.rules on the vm, and remove it’s entire contents, then restart the vm.