It is my understanding that when I enable Cisco Clean-Air on my 2602 AP's that currently host my SSID's it will still scan all channels. I spoke to a colleague who tells me that it will not scan all channels and instead will only scan the active channel. That colleague tells me that the only way for Clean-Air to scan all channels is for the AP to be dedicated for that purpose (Clean-Air).
By default I do believe it will indeed scan all channels. You can confirm this by going into the controller GUI under Wireless > 802.11a/n or 802.11b/g/n > RRM > General. Here you can specify if you want 'All Channels', 'Country Channels', or simply 'DCA Channels'.
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Local Mode AP (recommended) (LMAP)—A Cisco CleanAir AP operating in LMAP mode is serving clients on it’s assigned channel. It is also monitoring the Spectrum on that channel and that channel ONLY. Tight silicon integration with the Wi-Fi radio allows the CleanAir hardware to listen between traffic on the channel that is currently being served with absolutely no penalty to throughput of attached clients. That is line rate detection without interrupting client traffic.
There are no CleanAir dwells processed during normal off channel scans. In normal operation, a CUWN Local Mode AP executes an off channel passive scans of the alternate available channels in 2.4 GHz and 5 GHz. Off channel scans are used for system maintenance such as RRM metrics and rogue detection. The frequency of these scans is not sufficient to collect back to back dwells required for positive device classification, so information gleaned during this scan is suppressed by the system. Increasing the frequency of off channel scans is also not desirable, as it takes away from time that the radio services traffic.
What does this all mean?
A CleanAir AP in LMAP mode only scans one channel of each band continuously. In normal enterprise densities there should be plenty of APs on the same channel, and at least one on each channel assuming RRM is handling channel selection. An interference source that uses narrow band modulation (operates on or around a single frequency) is only detected by APs that share that frequency space. If the interference is a frequency hopping type (uses multiple frequencies – generally covering the whole band) it is detected by every AP that can hear it operating in the band.
__________________________________________________________________________________________ "Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin __________________________________________________________________________________________ "I'm in a serious relationship with my Wi-Fi. You could say we have a connection."
"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
Transferring Crash file from standby: Login to the Active WLC in HA.
From CLI: (Cisco Controller) >transfer upload datatype crash (Cisco
Controller) >transfer upload filename (Cisco
Controller) >transfer upload mode tftp (Cisco Controller) >transfer
This is the start of a display filter cross reference between Wireshark
and OmniPeek. The 1st installment is a table of advanced filters. More
filters will be added as time allows. It is a living doc, so check back
for changes every so often Please feel f...