"in theory, there's no difference between theory and practice. "

... but in practice, there is. - Jan van de Snepscheut

But in practice, theories are only hypotheses, which at best can just be falsified ;)

possibly misattrubited. https://en.m.wikiquote.org/wiki/Jan_L._A._van_de_Snepscheut

Going to come across as mean, but this post illustrates the difference between a sysadmin and a network engineer that specializes in things like this (and why you should not be using dumb unmanaged switches in an enterprise environment).

Remove the stuff about wireless repeaters and pallets of shampoo and this is a basic l2 loop that should have taken 10 minutes to track down.

Yes, as pointed out on many debugging stories: problems are easy to find if you look in the right place (hint: knowing where to look is the hard part). Unfortunately for the people living them, there are wireless repeaters and pallets of shampoo that make looking in the right place harder. You might as well have said that Waldo is easy to find if you remove all of the other people on the page.

As for it being "a basic L2 loop that should have taken 10 minutes to track down." If it were a "normal" L2 loop, and he could have taken 10 minutes tracking it down; sure. But when it only happens for ~2 minutes at a time, getting 10 minutes of actual tracking in is hard.

Sure, having managed switches would have made finding it easier. But most debugging stories have something that could have made them easier if done beforehand.

Knowing where the problem is, helps a lot. http://www.buzzmaven.com/2014/01/old-engineer-hammer-2.html