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Hello,

I just recently enabled some additional e-mail alerting from my cisco WLC. Since enabling them i've been receiving constant alerts about a  interferer 'WiFi Invalid Channel' being detected and then clearing.

the full message is

Security-risk Interferer 'WiFi Invalid Channel' is detected by 'WAP'.Interferer severity is '2'.

i've done some research on what this is, which from my understanding is either a non-wifi device or wifi device that is transmitting just off center of a standard wifi channel. However, i could not find anything on how to track down or locate these devices. any insight on how to do this would be appreciated.

Thanks

Break out the spectrum analyzer.

I would agree with mbsteez, unless the AP is really only telling you that a channel that it thinks shouldn't be in use is enabled somewhere.  In that case I would think the AP could be giving you more information itself.

I have every one of the Metageek Chanalyzers available at work and can attest to their great performance.   Heck, even their free InSSIDer tool might spot your problem.

We also have an older $80k+ Agilent SA, but forget trying to lug that around !   Any SA with a fast enough sweep, and adequate sensitivity (-85 dBm) that can see Bluetooth signals, should work fine. 

The 7dB Direction Finder antenna from MetaGeek also works well when attached to their little unit.  It has a good Front-to-Back ratio, and I have used it for preliminary antenna pattern testing in addition to its intended direction finding use.

just a quick update, i was never able to locate the source for the invalid channel alerts and disabled the alerting for these. The signal would show up for a couple of seconds and then disappear for awhile. While reviewing the invaild channel signals via Chanalyzer  it looked like it may have just been a corrupted signal.

Thanks for the replies on this.

Too bad you couldn't track it down.   It would have been interesting to see what caused it.

Unless you are a manufacturer and were testing some new firmware, I doubt it was a Wi-Fi device.

I see this in my environment. I haven't tracked it down beyond the same information that you all have posted. Seems to be the 2.4GHz frequency from the logs. I see it range from Channels 1, 6, and 11. 

LogSystem TimeTrap

0 Wed Apr 29 15:15:45 2015AP mmc-ag-nap24[0] (38:1c:1a:9b:d0:90) Device ID: 0x80d7, Type: WiFi Invalid Channel[31], Severity: 0, Channels: 6, Cluster ID: 03:a0:e0:00:14:21, Previous Cluster ID: 03:a0:e0:00:14:21, Event: Clear

1 Wed Apr 29 15:15:11 2015AP mmc-ag-nap24[0] (38:1c:1a:9b:d0:90) Device ID: 0x80d7, Type: WiFi Invalid Channel[31], Severity: 0, Channels: 6, Cluster ID: 03:a0:e0:00:14:21, Previous Cluster ID: 03:a0:e0:00:14:21, Event: Set

2 Wed Apr 29 15:09:36 2015AP mmc-ag-nap11[0] (38:1c:1a:9b:d5:60) Device ID: 0x9778, Type: WiFi Invalid Channel[31], Severity: 2, Channels: 6, Cluster ID: 03:a0:e0:00:14:1f, Previous Cluster ID: 03:a0:e0:00:14:1f, Event: Clear

BTW: Thanks for the advice on the Metageek Antenna. I was planning on tracking down a noise source in our ED and was thinking about a directional for the spectrum analyzer.