
NICs can take whole networks down
I once had a NIC go bad and take a whole network down. It was on a switch but that didn't isolate it. All the other computer's went off the network and nothing worked unless I shut everything down and powered back up. I had to power each computer off and check each one out until I found the problem. It was also intermittent at first.
A totally redundant link on all the computers could have still allowed operation, but it's also possible the bad link might have shut the other one down too. Off the shelf network gear might not solve this but one might need to design custom hardware to get past it. I suspect the industrial redundant ring switches like the ones from Sixnet would have still failed in this case.
Paris because she knows all about networking of videos.