After upgrade to Ubuntu 15.04, I see the same behavior with VirtualBox and VMWare Workstation. After the system is waked up from suspend, there's neither
vmnet8 devices in the output of
ifconfig. In the network menu, both virtual devices are marked as not managed.
In order to start the VMWare Workstation network, I have to
sudo service vmware restart. Then I see: "Connection Established. You are now connected to vmnet8".
In order to start the VirtualBox network, I go to
File -> Preferences -> Network -> Host-Only Networks -> vboxnet0.
Then press OK. I see "Connection Established. You are now connected to vboxnet0".
The question is, how to make virtual networks start automatically? It looks like a systemd issue since I haven't seen anything like that previously.