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Contributor I

5GHz channel changes every 10 seconds on IAP - is this normal?

Hello

 

I have a customer deployment running a few dozen Aruba Instant 6.5.1.0-4.3.1.0_57768 on AP 305's and their Airwave reports are telling me that the 5GHz radios are changing channels every 10 seconds due to "Channel Quality Threshold". 

 

The irony is that I would expect this to happen on 2.4GHz but those radios are quite stable (few changes per day perhaps).

I did some research and it appears that the IAP does not allow the settings  of any "thresholds" to influence this behaviour.

But then what "quality thresholds" are we even dealing with here?  How can I drill deeper for the root cause, other than to bring out the Sidekick and do a spectrum analysis?  It seems to be affecting the UNI-2 channels mostly - if this were a DFS issue then surely the IAP would have chosen a non-DFS channel ?.  What I am seeing is a constant flipflop of channel 100, 116, 100, 116 etc - every 10 seconds.  Maybe a bug?   The AP CLI commands via Airwave GUI don't seem to work too well because the IAP Virtual Controller is managed by Airwave.  I have not come across this before but I believe this is working as designed?

 

But  main point of my question is about these mystical thresholds.  Where can I find them, and can I tune them?

 

ARM flip flop.PNG

 

thanks in advance

Guru Elite

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

What is your channel width and your regulatory domain?

 

 


*Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.*
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Contributor I

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

Hi

 

On 5GHz 40Mhz is enabled (80Mhz disabled).  Australian regulatory domain (the Airwave interface for this VC under 'System -> General' is showing me that it's set for "Country Code Australia".  I have already spotted that the controller is choosing Ch128 which is not allowed in the AU domain.

However the other channels are valid and the AP is still flip flopping between the same ones every 10 seconds.

Guru Elite

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

In your screenshot, those are all DFS channels and that is unusual.


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Contributor I

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

Yes indeed. I will start by disabling those to see if things settle down. But why does ARM keep going back to those “bad” channels?
Guru Elite

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

execut  "show ap debug crash-info" and see if there is any information.


*Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.*
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Contributor I

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

Not having much joy with the show commands when the IAP's are being managed by AirWave. When I select an AP and run the command, it always tells me "no output for this command".  

 

***************************************************************************************************
show ap debug crash-info
No output for this command

 

Guru Elite

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

That means there are no crashes, which is good.

 

What are the allowed channels in your regulatory domain profile?


*Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.*
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Highlighted
Contributor I

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

Ha! That didn’t even occur to me because most commands have that same output.
Regarding regulatory domain, there is an issue. Customer selected ALL channels even a bunch hat are not allowed in the regulatory domain. I have asked them to please unselect those. Waiting for that to happen. And then I want to unselect DFS channels next.
Contributor I

Re: 5GHz channel changes every 10 seconds on IAP - is this normal?

I have an update

 

The problem all along seems to have been that Interference Immunity had been set to 0.  This had the following impact

1) 5GHz Channel flip flop every 10 seconds (always the same two channels)

2) Ignoring my channel configurations (e.g. when only allowing UNII1 and UNII3 channels, the AP would still assign every possible channel)

 

Once I set the Interference Immunity to the default of 2, then normality restored.  Suddendly ARM started assigning the correct channels within the allowed channels I configured.  And the channel flip flop stopped.

 

I have tried to read and understand what Interference Immunity does, but the standard Aruba documentation doesn't do a great job of explaining it. It think it deserves a longer discussion on its own about what each setting does and what the implications are. Aruba does state to leave that setting alone and it should be set under advisement.  I don't know why the customer has changed from the default - we may never know.

 

case closed

Regards

Arne

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