Cleints disconnected in AP-9136 model

[titusroz03]

Hello All,

We had several disconnections on wireless clients connected to one of our Access Points. Actual placement Map was like we have an AP over the ceiling mounted to provide coverage all over the region but this AP has a different RF group and policy tag and SSID

And the other AP which was placed on the desk/table rightaway below the ceiling AP and this has a different RF group,policy Tag and SSID.

Cleints were connected to this desk AP SSID and all of a sudden in a moment of 30-40 secs most of the clients got disconnected.

My Questions on this:

1. Since we have two Aps(Ceiling and desk) with different RF group, policy tag in same region, is there a chance of interference clash which could make the Radio unstable for the clients..?

2.By chance if we bring both the APs(celing and desk) into same RF group and Policy Tags with different SSID in the same placement as it is will that avoid these kind of disconnections..?

Kindly provide if you have any suggestions/comments on placing two Aps in same region ..? 

[Leo Laohoo]

What firmware is the WLC on?

What is the exact model of the WLC?

What is the uptime of the WLC?

How many APs are joined to the controller?

How many daily wireless clients are there?

Post the complete output to the following commands:

sh ap dot11 5ghz cleanair device type all 
sh ap auto-rf dot11 5
sh ap summary load-info

[titusroz03]

What firmware is the WLC on? 17.12.3

What is the exact model of the WLC?9800-L

What is the uptime of the WLC?- 1 yr.

How many APs are joined to the controller?More than 100

How many daily wireless clients are there? If you want the count of that particular Ap were clients got disconnected, it is around 25.

Post the complete output to the following commands:

sh ap auto-rf dot11 5 | b DESKAP01
AP Name : DESKAP01
MAC Address : e4a4.1cf3.1eb0
Ethernet MAC Address : e4a4.1ce8.6b8c
Slot ID : 1
Radio Type : 802.11ax - 5 GHz
Subband Type : All
Noise Information
Noise Profile : Passed
Channel 36 : -97 dBm
Channel 40 : -97 dBm
Channel 44 : -97 dBm
Channel 48 : -97 dBm
Channel 52 : -97 dBm
Channel 56 : -97 dBm
Channel 60 : -97 dBm
Channel 64 : -97 dBm
Channel 100 : -96 dBm
Channel 104 : -96 dBm
Channel 108 : -96 dBm
Channel 112 : -96 dBm
Channel 116 : -97 dBm
Channel 120 : -97 dBm
Channel 124 : -97 dBm
Channel 128 : -96 dBm
Channel 132 : -95 dBm
Channel 136 : -95 dBm
Channel 140 : -95 dBm
Channel 149 : -95 dBm
Channel 153 : -95 dBm
Channel 157 : -96 dBm
Channel 161 : -96 dBm
Channel 165 : -96 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 120 : -128 dBm @ 0% busy
Channel 124 : -128 dBm @ 0% busy
Channel 128 : -128 dBm @ 0% busy
Channel 132 : -128 dBm @ 0% busy
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)
Channel 36 : 0/ 0/ 0
Channel 40 : 0/ 0/ 1
Channel 44 : 0/ 0/ 0
Channel 48 : 0/ 0/ 0
Channel 52 : 0/ 0/ 1
Channel 56 : 0/ 0/ 0
Channel 60 : 0/ 0/ 2
Channel 64 : 0/ 0/ 0
Channel 100 : 0/ 0/ 0
Channel 104 : 0/ 0/ 0
Channel 108 : 0/ 0/ 0
Channel 112 : 0/ 0/ 1
Channel 116 : 0/ 0/ 0
Channel 120 : 0/ 0/ 0
Channel 124 : 0/ 0/ 0
Channel 128 : 0/ 0/ 0
Channel 132 : 0/ 0/ 0
Channel 136 : 0/ 0/ 0
Channel 140 : 0/ 0/ 0
Channel 149 : 0/ 0/ 0
Channel 153 : 0/ 0/ 0
Channel 157 : 0/ 0/ 0
Channel 161 : 0/ 0/ 0
Channel 165 : 0/ 0/ 0
Load Information
Load Profile : Passed
Receive Utilization : 0%
Transmit Utilization : 0%
Channel Utilization : 1%
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
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
AP e4a4.1cf0.dcef slot 1 : -33 dBm on (108, 40 MHz) (10.200.70.10)
AP e4a4.1cf0.e76f slot 1 : -40 dBm on ( 64, 40 MHz) (10.200.70.10)
AP e4a4.1cf0.c75f slot 1 : -43 dBm on (161, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.07df slot 1 : -43 dBm on ( 52, 20 MHz) (10.200.70.10)
AP e4a4.1cf2.f57f slot 1 : -48 dBm on ( 40, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.31af slot 1 : -50 dBm on (104, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.554f slot 1 : -51 dBm on ( 44, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.0c8f slot 1 : -53 dBm on (128, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.605f slot 1 : -54 dBm on (120, 40 MHz) (10.200.70.10)
AP e4a4.1cf2.ddaf slot 1 : -58 dBm on ( 44, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.518f slot 1 : -58 dBm on (128, 40 MHz) (10.200.70.10)
AP e4a4.1cf0.c8af slot 1 : -63 dBm on (104, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.452f slot 1 : -71 dBm on (132, 40 MHz) (10.200.70.10)
AP e4a4.1cf0.882f slot 1 : -76 dBm on (132, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.044f slot 1 : -77 dBm on (108, 40 MHz) (10.200.70.10)
AP e4a4.1cf2.d2cf slot 1 : -83 dBm on (161, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.15ef slot 1 : -84 dBm on (120, 40 MHz) (10.200.70.10)
AP e4a4.1cf3.61af slot 1 : -87 dBm on ( 40, 40 MHz) (10.200.70.10)
Radar Information
Channel changes due to radar : 0

DFS Statistics with Cisco Integrated RF ASIC
Filtered events on serving radio : 0
Filtered events on Cisco Integrated RF ASIC : 0
Triggered radar events : 0
DFS statistics last updated : 412395 seconds ago

Channel Assignment Information via DCA
Current Channel Average Energy : -85 dBm
Previous Channel Average Energy : -85 dBm
Channel Change Count : 0
Last Channel Change Time : 05/02/2025 10:32:08
Recommended Best Channel : 140
RF Parameter Recommendations
Power Level : 6
RTS/CTS Threshold : 2347
Fragmentation Threshold : 2346
Antenna Pattern : 0
Persistent Interference Devices
Class Type Channel DC (%%) RSSI (dBm) Last Update Time
------------------------- ------- ------ --------- ----------------
All third party trademarks are the property of their respective owners.

###################################################################

Number of Slots : 4
AP Name : HK-DESKAP01
MAC Address : e4a4.1cf3.1eb0
Ethernet MAC Address : e4a4.1ce8.6b8c
Slot ID : 2
Radio Type : 802.11ax - 5 GHz
Subband Type : All
Noise Information
Noise Profile : Passed
Interference Information
Interference Profile : Passed
Rogue Histogram (20/40/80)
Load Information
Load Profile : Passed
Receive Utilization : 0%
Transmit Utilization : 0%
Channel Utilization : 0%
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
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 changes due to radar : 0

DFS Statistics with Cisco Integrated RF ASIC
Filtered events on serving radio : 0
Filtered events on Cisco Integrated RF ASIC : 0
Triggered radar events : 0
DFS statistics last updated : 412395 seconds ago
RF Parameter Recommendations
Power Level : 0
RTS/CTS Threshold : 0
Fragmentation Threshold : 0
Antenna Pattern : 0
Persistent Interference Devices
Class Type Channel DC (%%) RSSI (dBm) Last Update Time
------------------------- ------- ------ --------- ----------------
All third party trademarks are the property of their respective owners.

[Leo Laohoo]

Remote into this AP and post the complete output to the command "sh file". 

[titusroz03]

Filesystem Size Used Available Use% Mounted on
devtmpfs 874.5M 0 874.5M 0% /dev
/sysroot 877.3M 206.7M 670.6M 24% /
tmpfs 1.0M 56.0K 968.0K 5% /dev/shm
tmpfs 877.3M 0 877.3M 0% /run
tmpfs 877.3M 0 877.3M 0% /sys/fs/cgroup
/dev/ubivol/part1 372.1M 68.1M 304.0M 18% /part1
/dev/ubivol/part2 520.1M 80.9M 439.3M 16% /part2
none 114.4M 5.8M 108.7M 5% /tmp
none 1.0M 56.0K 968.0K 5% /dev/shm

Can you clarify my above questions.

[marce1000]

  - Checkout :https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/217738-monitor-catalyst-9800-kpis-key-performa.html#toc-hId-866973845
              For instance : show wireless stats client delete reasons | e : 0

M.

[Leo Laohoo]

---

@titusroz03 wrote:

1. Since we have two Aps(Ceiling and desk) with different RF group, policy tag in same region, is there a chance of interference clash which could make the Radio unstable for the clients..?

---

There is one way to find out:  Turn off one of the APs and see if the disconnections go away.

[Saikat Nandy]

In addition to what @Leo Laohoo & @marce1000 said, let me try to put it in this way - 

My take on this:

1. Since we have two Aps(Ceiling and desk) with different RF group, policy tag in same region, is there a chance of interference clash which could make the Radio unstable for the clients..? Ans - As long as these 2 APs are in different channels, interference (specifically co-channel interference) is not going to happen. From the output I can see channel change is not happening as well - which says that DCA/ED-RRM is not considering channel change for this AP. On top of that if you look into the power level of DESKAP01 on 5Ghz, it is 6 --- which means your entire deployment is quite dense and the nearby AP table says that too....12 APs within -65dBm RSSI is 'really dense'.

2.By chance if we bring both the APs(celing and desk) into same RF group and Policy Tags with different SSID in the same placement as it is will that avoid these kind of disconnections..? Ans - Why would you like to keep 2 APs in the same area/space...one in ceiling and one in desk!! instead just use one AP and add the needed SSIDs in the Policy tag.

If you say all the clients connected to the AP dropped almost at the same time, there could be a chance of radio crash (just speculating). I believe the option for you here would be RA trace.

[titusroz03]

Hi Saikat,

Thanks for your inputs,I would like to clarify below points:

As you said power level seems to be 6 and it is considered as dense situation, what will be the best/standard power level to be usually in a AP..?

As you said we do see 12 Aps near, will this dense environment have a chance of disconnections like this..? Or what kind of risks are there if we run in this dense environment..?

We want to keep both the Aps because the one in celing have Guest network served and desk one have dedicated network for voice,each have invidual SSID and our plan was to not integrate both in Single AP..But as you suggested if we integrate both SSIDs in single AP,will there be any issues in the voice network..?

How many Max SSIDs(policy-Tags) can we have in single Ap..?

[Saikat Nandy]

Here are the answers to your questions - 

As you said power level seems to be 6 and it is considered as dense situation, what will be the best/standard power level to be usually in a AP..? Ans - There is nothing called best/standard power. TPC algorithm which falls under RRM is responsible for deciding the best power your AP can have (CHDM can also do to some extent). Which means, WLC will receive the NDP messages from all the AP...will run the TPC algorithm to decide what's the best power the AP can have...will ask the AP to increase/decrease the power level accordingly (happens in every 10mins). Now since WLC is deciding the power level 6 (in this case), does it mean that it is optimum?? The answer could be yes and could be no too. No because, APs are already running at the lowest power level (depending on model/regulatory domain). So if WLC/TPC decides that it is a dense environment and 6 is also loud, it does not have any further room to decrease the power level.

As you said we do see 12 Aps near, will this dense environment have a chance of disconnections like this..? Or what kind of risks are there if we run in this dense environment..? Ans - There can be multiple reasons for disconnections and we should not relate the disconnection with dense AP placement - unless we have solid proof. The right and first step to start troubleshooting disconnection, is to run RA Trace and see what is the client delete reason WLC is reporting. However this sorts of dense placement can impact your RF environment & client connectivity as well. Ex - your AP cells might overlap with each other 'too much' causing your end device to stick to one AP, although it is physically underneath an another AP. In other words roaming will be impacted. Dense AP deployment can inject co-channel interference as well is the channels are not distributed properly.

We want to keep both the Aps because the one in celing have Guest network served and desk one have dedicated network for voice,each have invidual SSID and our plan was to not integrate both in Single AP..But as you suggested if we integrate both SSIDs in single AP,will there be any issues in the voice network..? Ans - I am not seeing any issue to incorporate both the SSIDs in the same AP, unless you have very 'specific' use case.

How many Max SSIDs(policy-Tags) can we have in single Ap..? Ans - You can have maximum of 16 SSIDs under a Policy Tag. However lesser the number of SSID, better your wireless environment will be. That does not mean you should exclude your required SSIDs

As a side note - I don't know if any site survey has been performed before this deployment been done. If not, I would strongly suggest you to do that. Site survey team can ask you to limit the power level inside the RF profile so that AP cell don't bleed with each other.

[Rich R]

Just to add my bit - sudden disconnection of all clients on an AP is most likely going to be :
- radio crash/restart
- AP crash/reload
- AP CAPWAP restart causing AP to re-join the WLC
show ap uptime will quickly show you whether the AP has reloaded or re-joined.  If the AP crashed you should also see a APNAME.crash file on the WLC bootflash:
For radio crashes or restarts you'll need to look at the logs on the AP (show logging) and show flash crash

Take note of the TAC recommended code versions (link below) to make sure you have fixes for numerous known bugs.
And check your WLC config with the Config Analyzer (link below) using the output from "show tech wireless"  This will highlight many common config errors and best practices.