Very often, ESXi will lose network connectivity (mostly when trying to reset a VM or something).
As I had passthrough of gpu enabled, I could not get to the console to check what's going on.
I disabled gpu passthrough, and as soon as the box lost network connectivity again, I went to the host console.
It appears ESXi itself is frozen, and does not respond to the keyboard at all. No errors, nothing.
Any ideas?