Wireless installations APs slowly ALL move to non-DFS channels

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Hi,

Have an issue with wireless installations in that all the careful 5Ghz channel planning that goes into the design, over a number of days, weeks and months, all the channels slowly end up moving to only the 4 available non-DFS channels, due to DFS events like the below:

Device: 10.23.23.11
Severity: Warning
Message: AP Serial Number 1628Y-1031700000: Radar found on channel 5540Mhz DFS Channels/Frequencies:
Channel 52 : 5260
Channel 56:  5280
Channel 60:  5300
Channel 64:  5320
Channel 100: 5500
Channel 104: 5520
Channel 108: 5540
Channel 112: 5560

Device: 10.23.23.11
Severity: Warning
Message: events:  Access Point AP Serial Number 1608Y-1041000000: Radar found on channel 5560Mhz 2 DFS Channels/Frequencies:
Channel 52 : 5260
Channel 56:  5280
Channel 60:  5300
Channel 64:  5320
Channel 100: 5500
Channel 104: 5520
Channel 108: 5540
Channel 112: 5560

This is happening regardless of location or installation, and is likely because of legitimate DFS events that are being picked up in the air that I have no control over. 

Radar always seems to be detected on difference frequencies, and it seems to affect just a few APs at a time until all the APs are on non-DFS channels.

Initially I was tackling this by creating a 2-channel plan, one which used all the 5GHz channels, and one with just non-DFS. This meant that when a DFS event happened I could at least be predictive as to what non-DFS channel the AP when to.

So there are several problems with this:

1) The first is that I would have to manually go to the configuration of each AP and then set the channel back every couple of months, which with several hundred APs this just become to time consuming, and unpractical to do.

2) The other option is to put the APs into dynamic channel select mode, say over the weekend, let them fight out a channel plan and turn it off before the beginning of the week - as per the method in the article below:

https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-configure-APs-to-Channel-Select-to-...

What I would like to know is what other methods there might be to help assist this situation, here is a few I would like:

1) Preferred channel - so if the channel does change to a non-DFS channel that either through a reboot, schedule maintenance time, or after a pre-determined amount of time the channel moves back. My 2-channel plan would then work quite nicely.

2) That DCS can made active at a certain time, for a certain period of time so that channels can be automatically reorganised to best occupy the full amount of channels. For this I had considered leaving DCS on but setting the period in minutes to happen in the middle of the night, but not sure if that's a good idea.

Many thanks in advance.
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Martin Flammia

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Posted 1 year ago

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Ostrovsky, Yury, Employee

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Hi Martin. Your suggestion #1 is good, and I believe our product management looking into this option to include it at some point.
As for the second suggestion, you can use the script to schedule the DCS at certain period of time. Script should be already available at ExtremeManagement if you have one.
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Martin Flammia

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Excellent - hadn't noticed that script had existed.

Will give that a go. Thanks.

If the first option ever happens, or there is an ETA then please post back as would be interested in it. Cheers.
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Martin Flammia

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So here is the million dollar question....

Do I either just hard-code all APs to just non-DFS channels, this I imagine wouldn't be the recommendation as you restricted to such a small set - we have heard this as being the preferred method though?

or, Do I run the DCS script scheduler, either each evening, or the end of each week to straighten out the channels again. This though has a detrimental effect in that on the proceeding day particularly a lot of APs move to non-DFS channels, which will effect users currently attached.

To me it seems the later is the lesser of the two evils, but interested in the communities suggestions.

Many thanks.
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A.Kue

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We have the same problem on our campus network. Due to a complex channel-plan in our high-density environment, which is constantly ruined by the mentioned radar-detection, DCS is not an option.

If the APs would, at least, switch to the preferred channel after reboot, we could deal with this workaround. Cisco just uses a "prefer_channel return-time" option to avoid that issue. It would be nice to see something similar on Extreme Wireless.
(Edited)
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Ronald Dvorak, Embassador

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What AP models are used, I've the same issue and for me it looks like that some AP models are more sensitive to radar then others.

-Ron
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A.Kue

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We have solely AP3825i in use.
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Ronald Dvorak, Embassador

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Could you please also tell me the software version that is running and the country.
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A.Kue

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Model AP3825i
Software Version 10.21.04.0005
Country Germany