Jonathan D. was the system administrator for a school nestled in a war-ravaged city somewhere in the middle of the desert. What with bombings here, explosions there, and the odd RPG whizzing by, dealing with a converted bathroom as an office/datacenter just didn't seem to be all that big of a deal.
The school had roughly 100 computers split between two buildings, along with the laptops everyone used. His office, ...erm... converted bathroom housed all of the servers, and the main computer room for the high school/middle school (grades 6 and up) building was located right outside the door.
One morning, as the sun came up over the desert, he found that he was unable to connect to the internet. After trying to ping the gateway and getting no response, Jonathan tried pinging the data servers. Nada.
When he did a visual inspection of the servers which revealed that they looked fine, he thought that maybe the problem was with his desktop. While it was rebooting, he heard the volume of the students in the computer room explode. The computers in there were no longer able to see the server and had hung.
At this point, Jonathan knew the problem wasn't just with his desktop. If the computer room next door couldn't reach the servers right next to them, then the odds of any of the other computers further out being able to get through were pretty much nil. The network was down for the whole school. Had there been an attack?
Rebooting the (unmanaged) switches in his
bathroom office yielded nothing useful. Finally, in desperation, he disconnected the servers and the computer room from the rest of the school. Shouts of victory arose from the computer room; they were able to work again!
Now he had to figure out where the problem was rooted. Jonathan isolated one switch at a time, working his way through the school until he had reached the computer room in the elementary building (grades 1-5). With some help from the technician in the computer room, he was able to identify one of the switches as being the cause of the problem.
He unplugged the ports in the switch, one at a time, until he noticed something strange. As he unplugged each port, both its light and the light below turned off. When he plugged it in again, both lights came back on.
"What's plugged into this port?" he asked the technician.
"Nothing! We don't have any computers plugged into that socket," he replied.
"Well something's plugged into it. Let's go take a look."
They walked over to the other end of the cable in the computer room and saw that a teacher had set up a little work area with a box of papers and some pens. When they moved the box out of the way, they found... a network cable plugged into the socket... and the other end plugged into the neighboring socket.
They talked with the teacher who had set up the work area, and found out that he normally brought in his laptop, along with a network cable. On this particular day he'd left the laptop at home, and he wanted to clean his workspace. He decided to tidy up the network cable by plugging both sides in, creating a feedback loop, which caused a network storm and wound up taking down the whole network.