The wireless bridge that links this U.K. school's network with some remote classrooms has stopped working, says a network admin pilot fish working there -- but that's not the really puzzling part.
"It looks like the access point in the remote classroom is down for some reason, which of course means I can't get to the web or console interfaces to check it out," fish says.
"The strange part, though, is that I can still ping it via its IP address -- even when it's unplugged, powered down and sitting on my desk (I wanted to make absolutely sure I wasn't just pinging the access point)."
Fish quickly concludes there's an IP conflict, which may have been messing up the Wi-Fi bridge.
And thus the hunt for the rogue IP address begins. Fish manages to get the MAC address through packet inspection. He checks out the prefix, but it belongs to some manufacturer he's never heard of who provides hardware for all the big vendors -- no help there.
Eventually he gets permission to start unplugging switches one at a time until the address stops pinging -- which it does when fish disconnects the IT offices.
But with a little more effort he tracks it down. The problem address isn't in IT -- it's in the head teacher's office, which is next door and patched into the same switch.
Turns out the head's laptop, like all the school management's computers, was set up and is managed by engineers working for the county council -- and they don't feel the need to coordinate with the school's techs when they change something. They also didn't ask whether the IP address they gave the laptop, apparently at random, was already in use.
"So with the head's laptop unplugged, I am able -- five hours later -- to go back to the access point and confirm it's broken and will need to be replaced," says fish.
"But at least I've sorted out an IP conflict that managed to fly under the radar for eight months."
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