When installing VirtualBox, it presents a warning that "Installing the Oracle VM VirtualBox Networking feature will reset your network connection and temporarily disconnect you from the network."
But does this refer to their network cards, i.e. disconnecting only guest VMs, or do they mean the real network cards in the host device itself?
It didn't seem to disconnect my real cards, but I'd like to ask to be sure it's intentional.
It is totally intentional. It has to disable (briefly) all network interfaces in order to insert the special filter driver in the network stack that is needed to merge the VM traffic with the normal data-stream on the interface.
It is short enough that it is often not noticeable, so you may not have noticed it before, but it depends highly on what you are doing with the NIC at the time.
If you have some program running that is quite sensitive to network interruptions (like a VOIP or Skype call or, in a business environment, SAP clients) you will notice a hiccup or even a full disconnect.
