Monday, September 19, 2011

The Amazing, Disappearing SSID

Lately, after running dependably for several years, my wireless access point has started to disappear from the airwaves.

Firmware upgrade? Got it, no luck. I went from rev 1.0 (2006) to rev 2.12 (2009) with the same issue.

Here's an odd side effect: while troubleshooting this problem, I've been running airodump-ng on a wired PC. Normally I can "see" ~16 access points. When my access point dies, it takes about a dozen with it. When I bounce it, they all come back.

WTF is up with that? It's probably no big mystery. I'm assuming that the radio pulse from my access point coming back online somehow boosts the sensitivity of the NIC running airodump, but it's a strange process to watch.

I have responded to this by writing a kidscript that runs iwlist on another PC. If it finds that the SSID is not being broadcasted, it runs a quickie curl one-liner that presses the "Apply" button on the "Advanced Settings" page of the access point's Web config, which acts like a soft reboot. The process repeats every ten minutes with a cron job.

This is entirely unacceptable! In the past I've had laptops connected wirelessly for days without interruption. On version 1.0 of the firmware!

Since it's seen Better Days, I have to assume it may just be going bad, although in my testing I have made it fail reliably at definite intervals (long story). With that in mind, I've ordered a replacement. If that one works, great.

If not, then there must be a mystery somewhere.

I hate mysteries.

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