I have a Virtualbox instance running the latest Ubuntu hosted on OSX. Things worked fine until today when, for no apparent reason, Ubuntu stopped raising the network card on startup.
I've fiddled with all network options in VirtualBox but nothing seems to work.
How can I troubleshoot this?
Added as suggested:
I can see eth0, but it has no IP is assigned. Could the problem be with the router, to which I do not have access?