Find the fault
Six failures that have taken real shows down. Each one is investigated by choosing what to look at, in the order you choose to look at it — and that order is the thing being practised, because naming the fault after forty minutes of guessing is not the same as finding it.
Every step costs you something. Some tell you a great deal. Some tell you nothing at all, and those are in the list precisely because they are the ones people reach for first.
Nothing here is scored or stored. There is no streak and no badge. A drill you are being marked on is a test, and on a test people stop taking the risks that teach them anything. What you get back is a sentence about how you worked, which is the only part worth having.
Work bottom-up: physical, addressing, reachability, protocol, software. The link light is thirty seconds and rules out the largest fault family there is. Reinstalling the software is forty minutes and rules out almost nothing. The field card has the commands.
If it has a signature — something that distinguishes it from the four things it looks like — it belongs here. Describe it, including the steps that wasted your time, because those are the half that makes a scenario teach anything.