High Channel Utilzation on 5Ghz with no Client connected

[janvelgado_16]

Hi guys,

I am just wondering, no client is connected on 5GHz and yet there is a very high channel utilization with 0% interference. Do you know how is that possible? no problem on 2.4GHz. Im using Cisco WLC 5520 and firmware version 8.2. Is this some kind of bug?

My troubleshooting procedure on that is restart the AP and the channel utilization returns to normal. Please see attached photo.

Thank you for the help,

JE

[Scott Fella]

Sure looks like a bug. We have controllers on v8.2.110.0 and v8.2.130.0 and don't see that issue.  I have seen high channel on v8.0.111 code but when there were more than 10 clients which was a bug in that version.  If you look at the show ap auto-RF 802.11a <ap name>, do you see high utilization also.  If so, then either open up a TAC case or try a different code version to compare. 

-Scott

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[janvelgado_16]

Hi Scott,

Thanks for that. Can you look at these, here is the output of the command and another AP on high Utilization. Should I open a TAC Case?

(Cisco Controller) >
(Cisco Controller) >show ap auto-rf 802.11a T1-00-001

Number Of Slots.................................. 2
AP Name.......................................... T1-00-001
MAC Address...................................... dc:ce:c1:2c:36:70
Slot ID........................................ 1
Radio Type..................................... RADIO_TYPE_80211a
Sub-band Type.................................. All
Noise Information
Noise Profile................................ FAILED
Channel 36................................... 17 dBm
Channel 40................................... 17 dBm
Channel 44................................... 17 dBm
Channel 48................................... 17 dBm
Channel 52................................... 14 dBm
Channel 56................................... 14 dBm
Channel 60................................... 14 dBm
Channel 64................................... 14 dBm
Channel 100.................................. 14 dBm
Channel 104.................................. 14 dBm
Channel 108.................................. 14 dBm
Channel 112.................................. 14 dBm
Channel 116.................................. 14 dBm
Channel 132.................................. 13 dBm

--More-- or (q)uit
Channel 136.................................. 13 dBm
Channel 140.................................. 13 dBm
Channel 149.................................. 13 dBm
Channel 153.................................. 13 dBm
Channel 157.................................. -89 dBm
Channel 161.................................. 13 dBm
Channel 165.................................. 13 dBm
Interference Information
Interference Profile......................... PASSED
Channel 36................................... -128 dBm @ 0 % busy
Channel 40................................... -128 dBm @ 0 % busy
Channel 44................................... -128 dBm @ 0 % busy
Channel 48................................... -128 dBm @ 0 % busy
Channel 52................................... -128 dBm @ 0 % busy
Channel 56................................... -128 dBm @ 0 % busy
Channel 60................................... -128 dBm @ 0 % busy
Channel 64................................... -128 dBm @ 0 % busy
Channel 100.................................. -128 dBm @ 0 % busy
Channel 104.................................. -128 dBm @ 0 % busy
Channel 108.................................. -128 dBm @ 0 % busy
Channel 112.................................. -128 dBm @ 0 % busy
Channel 116.................................. -128 dBm @ 0 % busy
Channel 132.................................. -128 dBm @ 0 % busy

--More-- or (q)uit
Channel 136.................................. -128 dBm @ 0 % busy
Channel 140.................................. -128 dBm @ 0 % busy
Channel 149.................................. -128 dBm @ 0 % busy
Channel 153.................................. -128 dBm @ 0 % busy
Channel 157.................................. -128 dBm @ 0 % busy
Channel 161.................................. -128 dBm @ 0 % busy
Channel 165.................................. -128 dBm @ 0 % busy
Rogue Histogram (20/40/80/160)
.............................................
Channel 36................................... 0/ 0/ 0/ 0
Channel 40................................... 0/ 0/ 0/ 0
Channel 44................................... 0/ 0/ 0/ 0
Channel 48................................... 0/ 0/ 0/ 0
Channel 52................................... 0/ 0/ 0/ 0
Channel 56................................... 0/ 0/ 0/ 0
Channel 60................................... 0/ 0/ 0/ 0
Channel 64................................... 0/ 0/ 0/ 0
Channel 100.................................. 0/ 0/ 0/ 0
Channel 104.................................. 0/ 0/ 0/ 0
Channel 108.................................. 0/ 0/ 0/ 0
Channel 112.................................. 0/ 0/ 0/ 0
Channel 116.................................. 0/ 0/ 0/ 0
Channel 132.................................. 0/ 0/ 0/ 0

--More-- or (q)uit
Channel 136.................................. 0/ 0/ 0/ 0
Channel 140.................................. 0/ 0/ 0/ 0
Channel 149.................................. 0/ 0/ 0/ 0
Channel 153.................................. 0/ 0/ 0/ 0
Channel 157.................................. 0/ 0/ 0/ 0
Channel 161.................................. 0/ 0/ 0/ 0
Channel 165.................................. 0/ 0/ 0/ 0
Load Information
Load Profile................................. FAILED
Receive Utilization.......................... 0 %
Transmit Utilization......................... 97 %
Channel Utilization.......................... 97 %
Attached Clients............................. 0 clients
Coverage Information
Coverage Profile............................. PASSED
Failed Clients............................... 0 clients
Client Signal Strengths
RSSI -100 dbm................................ 0 clients
RSSI -92 dbm................................ 0 clients
RSSI -84 dbm................................ 0 clients
RSSI -76 dbm................................ 0 clients
RSSI -68 dbm................................ 0 clients
RSSI -60 dbm................................ 0 clients

--More-- or (q)uit
RSSI -52 dbm................................ 0 clients
Client Signal To Noise Ratios
SNR 0 dB.................................. 0 clients
SNR 5 dB.................................. 0 clients
SNR 10 dB.................................. 0 clients
SNR 15 dB.................................. 0 clients
SNR 20 dB.................................. 0 clients
SNR 25 dB.................................. 0 clients
SNR 30 dB.................................. 0 clients
SNR 35 dB.................................. 0 clients
SNR 40 dB.................................. 0 clients
SNR 45 dB.................................. 0 clients
Nearby APs
Radar Information
Channel Assignment Information
Current Channel Average Energy............... 32 dBm
Previous Channel Average Energy.............. 32 dBm
Channel Change Count......................... 1104
Last Channel Change Time..................... Thu Oct 6 09:40:36 2016
Recommended Best Channel..................... 157
RF Parameter Recommendations
Power Level.................................. 1
RTS/CTS Threshold............................ 2347

--More-- or (q)uit
Fragmentation Threshold...................... 2346
Antenna Pattern.............................. 0

Persistent Interference Devices
Class Type Channel DC (%%) RSSI (dBm) Last Update Time
------------------------- ------- ------ ---------- ------------------------
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(Cisco Controller) >

Regards,

JE

[Scott Fella]

I would open a TAC case. I noticed that you are using an 1800 AP and it can be a bug on that. Again, I'm running probably a different code that you but also I am using a 3602, 3702 and 3802 and don't see that issue on the code versions I mentioned. What code are you running and what controller?

-Scott 

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[janvelgado_16]

Scott,

We are running a 5520 WLC (redundant) with version 8.2.111.0. is this an AP bug or WLC bug? will open a TAC Case.

[Scott Fella]

Well... might be a bug. I know that some whom ran that code has had issue. 8.2.100.0 was fine for us and we are running 8.2.110.0 on a few 5520's in SSO but we don't have the 1800 AP's. 

Open a TAC case and let them investigate while you test or look at upgrading which they might tell you anyways. 

-Scott 

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[janvelgado_16]

Thanks Scott, I will let you know once we have further investigated this issue with TAC. 

JE

[janvelgado_16]

Hi All,

As confirmed with TAC, it is indeed a bug issue. See link: https://tools.cisco.com/bugsearch/bug/CSCuy97681/

Recommended action is to upgrade the WLC to the following 8.2.130.0.

https://www.cisco.com/c/en/us/support/docs/wireless/wireless-lan-controller-software/200046-TAC-Recommended-AireOS.html?cachemode=refresh#anc8

Thank you all,

JE

[Scott Fella]

Thanks for the update!

-Scott 

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[Leo Laohoo]

Recommended action is to upgrade the WLC to the following 8.2.130.0.

Thanks for the update.  

This doesn't make sense.  None at all.  

Did TAC provided this recommendation, upgrade to 8.2.130.0?  

If they did then I'd request the case to be escalated.  According to the Release Notes of 8.2.130.0, Bug ID CSCuy97681 isn't even listed as either OPEN or Resolved Caveats.  

The details of the bug also identifies the bug to be found in 8.2.100.0 but the controller is running 8.2.111.0.  Another thing, the bug details also states "No release planned to fix this bug".  

Upgrading to 8.2.130.0 may not fix the issue but TAC can provide you with an engineering version which may include a fix to this bug.

[janvelgado_16]

Thanks Leo, Salamat ng marami

Indeed TAC has recommended that, herewith below is his email:

"After checking on my I found that we had a bug with same symptoms (now it’s closed since the issue is not reproducible on the latest 8.2 release)   https://tools.cisco.com/bugsearch/bug/CSCuy97681/

So can you please upgrade your WLC to the following recommended release 8.2.130.0: https://www.cisco.com/c/en/us/support/docs/wireless/wireless-lan-controller-software/200046-TAC-Recommended-AireOS.html?cachemode=refresh#anc8"

I have asked TAC your reply on this thread. 

Thank you so much,

JE

[Leo Laohoo]

Channel 157.................................. -89 dBm

This is pretty high.  What happens if you disable Channel 157?

[janvelgado_16]

Sorry Leo, but what does that value means? All other values for Noise profile are + dBm.

[Leo Laohoo]

Channel 36................................... 17 dBm
Channel 40................................... 17 dBm
Channel 44................................... 17 dBm
Channel 48................................... 17 dBm
Channel 52................................... 14 dBm
Channel 56................................... 14 dBm
Channel 60................................... 14 dBm
Channel 64................................... 14 dBm
Channel 100.................................. 14 dBm
Channel 104.................................. 14 dBm
Channel 108.................................. 14 dBm
Channel 112.................................. 14 dBm
Channel 116.................................. 14 dBm
Channel 132.................................. 13 dBm
Channel 136.................................. 13 dBm
Channel 140.................................. 13 dBm
Channel 149.................................. 13 dBm
Channel 153.................................. 13 dBm
Channel 161.................................. 13 dBm
Channel 165.................................. 13 dBm

Duhhhh ... I made the wrong assumption.  These values are the very high.  

I'm with Scott.  This could be a bug.  

[GC013]

Hi guys,

I'm having similar issue. We have 320 AP's in different buildings, and running the following WLC:

Cisco IOS XE Software, Version 17.03.05a
Cisco IOS Software [Amsterdam], C9800 Software (C9800_IOSXE-K9), Version 17.3.5a, RELEASE SOFTWARE (fc2)

DNAC is giving us P3's almost everyday on around 35 AP's.

Here is an example:

Anyone have this issue with this WLC version?

Thanks in advance for any tips and advice.