I work at a few large retail stores, and last week all the workstations lost access to the network, at one of the stores I work at.
I go to different stores every day on a weekly schedule.
I was busy at the time so I didn't really look into it, and the store called in Nerds on Wheels to fix the problem.
All the wireless devices on the network still worked though, so all the employees were using these to access the computer.
It took the NERD 4.5 days to finally figure out that the hub connecting the workstations had died.
LOL, there's money well spent!!