netcurmudgeon (netcurmudgeon) wrote,

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Some you win, some you don't know why

I had one of those not particularly satisfying troubleshoots this morning. The T1 router at Classical Magnet School that handles VoIP traffic crashed yesterday at 16:30. The router that handles data traffic was still up, so I tried a couple of things remotely last night – including commanding the UPS units that power the network equipment to restart, hoping that a power reset would clear the router problem – all to no avail.

So, this morning I trundled out to Classical to have a look at the balky router. When I got there the router's fault light was on and it wasn't doing anything. I hooked up my laptop to the console port and power-cycled it. No dice. Not even a peep. I pulled the router out of the rack. Normally the router's motherboard is green, with a mix of black and shiny metal chips. Not this one. There was a thick layer of construction dust inside, making it an even dusty brown. I blew all the dust out that I could and powered it up.

Viola! The router started up, ran through its self tests and, and came to a ready prompt. I turned it off, pulled the RAM out, blew it off, stuck it back in, and hit the power again. The second startup was fine as well, so I powered it off and stuck it back in its casing in the rack, connected the cables and started it up.

Dust. Mark-my-unindicted-co-conspirator and I have three possible hypotheses:

• The dust (which has a pretty high R value) was creating a high-temperature condition which caused the router to shut itself down.

• The dust, which is construction dust and includes dust from demolition and things like duct construction, may have had a sufficient metallic content to cause current leakage across legs on the chips, causing the crash.

• It rained like crazy yesterday – perhaps the dust soaked up enough moisture to generate shorts across some of the chips, causing the crash.

In all of these cases, blowing off the dust removes the problem. So, I'll never know what the true cause was.

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