ACSP - Auto Channel selection doesn't appear to be working.

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  • Updated 3 years ago
Currently our radio profiles are set to perform Automatic Channel selection between the hours of 04:30 and 05:30 everyday. However, in some instances, some of the AP's assign themselves the same channel (even though they are in close proximity to one another). Is this due to AP placement or are there other factors that could be at play here?
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Luke Harris

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Posted 3 years ago

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Brian Powers, Champ

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A show acsp channel-info detail will actually show some of the values that the APs take into account when choosing which channel to use.

There is a chance that they are seeing something that you are unaware of that is causing them to end up on like channels.  Feel free to post the output of the "show acsp ch de" command and we can try to make sense of it.
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Mike Kouri, Official Rep

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Luke,
It's possible you did everything right. We have seen this in few unique deployment scenarios, we acknowledge that there is a room for improvement in our channel selection algorithms and we are taking steps to remedy that in an upcoming release. 
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Luke Harris

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Brian, would you like the whole output or just the channels that we actually use (1-5-9-13). Unsurprisingly the 5GHz band is free of channel clashing.
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Brian Powers, Champ

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You can dump it all here if you want.  The other channels will have a weighted value of like 32k based on the radio profile eliminating them from ever being used, but we may see something useful on some other statistics on those channels.
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Luke Harris

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Here we are Brian, hopefully you can make sense of this!




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Brian Powers, Champ

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May not make complete sense of it, but its a piece of the puzzle.

With the high CU (channel utilization) on channels 2 and 3, I suspect the APs are avoiding channel 1.  The high CU on 6 and 7 may also be causing channels 5 and 9 to be avoided.  Are your APs predominantly sticking to channel 13?  Both 13 and 5 actually show the lowest probability factor, which is the value used to select the channel based on all of the factors there I believe.

When you do a "show acsp neighbor" what does your RF environment look like there?  Are you in a highly congested RF area?  
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Luke Harris

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Your explanation of the CU definitely makes a lot of sense, certainly gives insight into how channels are distributed. 

Looking at the output from this AP and knowing it's approximate location I would say that it is within a fairly densely populated area. However distribution of channels between AP's seems consistent. Is there any benefit to statically configuring channels and power settings?
(Edited)
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Brian Powers, Champ

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Statically assigning channels and power settings can be a double edged sword.  As environmental factors our of your control (other RF networks mainly) change, with statically assigned settings, your WLAN will be stagnant in the environment.  With things set automatically, it would have the ability to adapt to the surrounding and hopefully select the cleanest channels based on what it hears around it.

I'm all for statically assigning power settings (or at least setting a max limit within the radio profile) to control somewhat your RF cell.  Statically assigning channels though has to be done with caution and monitored on occasion as things can and do change outside of your control (especially if you are in an area with lots of other businesses that have wireless networks).

Going back to your acsp channel-info detail images, any idea what is causing the high channel utilization on those off channels (2, 3, 6 and 7)?  
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Luke Harris

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The AP's are situated within a student residential block - so the list of personal and domestic devices that could be utilising those channels could be quite large...and also difficult to detect. We've had issues before where students have started using personal routers (another story) but these are always picked up by our AP's and are easily mitigated.