Wireless Access

It must be somehow in the beacon I guess.

The reason I asked this is becasue I had a one time situation where about 450 users where contected to controller and 90% of them where not band steered to 5Ghz and I noticed that majority of client's radio capabilites where 2.4 when I know most of them were 5Ghz. After reboot of all RAPs problem disappeard.

The controller would discover capability quicker in a dense AP environment.  Access points would crowdsource different channels and observe associations more easily in that environment.  In a single-ap environment there are many fewer opportunities to discover client capabilities, because clients only scan when they are disconnected searching for an access point or when they are attempting to roam. 

That was dense enviroment it happend when about 200 users came in relatively short period of time and I wanted to change from aggressive to normal ARM profile settings for A band but mistakenly applied "regular" settings you see below to G.

You should have no real need to change the ARM defaults, besides client-aware.  If you have plenty of data being transmitted by your clients to your access points, access points will defer scans (load aware scanning), so it could take longer to identify 5ghz-capable clients.  It is much better to ensure that the 5ghz ARM tx power range is 6db higher than the 2.4ghz ARM tx power range to ensure that clients choose the 5ghz band.

Again, there is no real advantage to changing the ARM settings from the defaults.  Transmit power difference between the 2.4ghz and the 5ghz band has a more immediate and lasting effect on what band dual-band clients connect to.

the dual band capable "flag" as seen by client match comes from probes, if a client doesnt probe on 5ghz "at least once" then it will never be marked as dual band, and thus never bandsteered.

many mobile devices wont probe until quite low signal, -75 dBm, which when combined with too high tx power, and/or not enough offset from 2.4ghz to 5ghz (as Colin mentioned) can combine to create the kind of problem that you saw.

back off the 2.4ghz power significantly, offset the max power in the 2.4ghz arm profile from the min power of the 5ghz arm profile by 6 to 9dBm and remove out the 11b rates and see how that goes

you can measure the result from the summary at the end of "show ap association [remote]" which shows "Total num of dual-band capable clients in 2.4G band"

Thank for explaining how controller discovers capability.

Power settings were not a problem. I knew it worked fine day before and even the morning I started playing with reverting agressive settings in order to move from enviroment of fast radio auto adjustment into regular one. My understanding was that my profile for G was basically the same I mistakenly paste above config so it should not affect the situation in any way

My power was set always like that for this setup and it worked fine almost all the time.

A - was 9-18

G -was 3-9

Please open a TAC case. There are quite a few factors that could affect what you are doing.

"I started playing with reverting agressive settings in order to move from enviroment of fast radio auto adjustment into regular one. My understanding was that my profile for G was basically the same I mistakenly paste above config so it should not affect the situation in any way" - This is not true.  Clients ultimately make the decision and changing settings in the infrastructure might or might not have an effect.  The infrastructure can only influence client decisions and not control them.  If a client is already associated, changing aggressive settings might not have any effect on already associated clients.  Please open a TAC case so that they can provide you guidance about what you are seeing.

Scary thing happend again, out of nowhere, in the middle of the day, no changeds were made. Issue was reported to me people could not connect it it was obvious why, whoever could was forced to 2.4.

All channles 20Mhz, 2.4 power bracket way lower than 5

First picute numbes were even worse in favor of 2.4 number like 200/60

All ap here are RAP setup

problem started out of nowhere forcing majority of clients into 2.4 unrecognizing them as valid 5ghz capabale

all back to normal 30 later

That shows how when sth happens out of nowhere clients flowing from 5ghz into 2.4ghz

I went back to slighlty adusted default settings that I thought were safer in my case but that did not prevent this from happening

Channel width were 20Mhz before so I dont conisder this as a cause

show rf arm-profile default-a

Adaptive Radio Management (ARM) profile "default-a" (Predefined (changed))
--------------------------------------------------------------------------
Parameter                                                                    Value
---------                                                                    -----
Assignment                                                                   single-band
Allowed bands for 40MHz channels                                             a-only
80MHz support                                                                Enabled
160MHz-support                                                               None
Client Aware                                                                 Enabled
Max Tx EIRP                                                                  21 dBm
Min Tx EIRP                                                                  12 dBm
Rogue AP Aware                                                               Disabled
Scan Interval                                                                10 sec
Aggressive scanning                                                          true
Active Scan                                                                  Disabled
ARM Over the Air Updates                                                     Enabled
Scanning                                                                     Enabled
Multi Band Scan                                                              Enabled
VoIP Aware Scan                                                              Enabled
Power Save Aware Scan                                                        Disabled
Video Aware Scan                                                             Enabled
Ideal Coverage Index                                                         10
Acceptable Coverage Index                                                    4
Free Channel Index                                                           25
Interfering AP Weight                                                        25 %
Backoff Time                                                                 240 sec
Error Rate Threshold                                                         70 %
Error Rate Wait Time                                                         90 sec
Channel Quality Aware Arm                                                    Disabled
Channel Quality Threshold                                                    70 %
Channel Quality Wait Time                                                    120 sec
Minimum Scan Time                                                            8
Load aware Scan Threshold                                                    1250000 Bps
Mode Aware Arm                                                               Disabled
Scan Mode                                                                    all-reg-domain
Client Match                                                                 Enabled
Client Match Report Interval (sec)                                           30
Allows Client Match to Automatically Clear Unsteerable Clients after Ageout  Enabled
Client Match Unsteerable Client Ageout Interval                              2 Days 0 Hours
Client Match Band Steering G Max Signal (-dBm)                               45
Client Match Band Steering A Min Signal (-dBm)                               75
Client Match Sticky Client Check Interval (sec)                              3
Client Match Sticky Client SNR (dB)                                          18
Client Match SNR Delta Bound(dB)                                             10
Client Match Sticky Min Signal                                               65
Client Match Steering Timeout (sec)                                          10
Client Match Load Balancing Threshold (%)                                    20
Client Match IOS Steering Backoff Interval (sec)                             300
Client Match VBR Stale Entry Age (sec)                                       120
Client Match Max Steering Failures                                           2
Client Match Load Balancing Client Threshold                                 30
Client Match Load Balancing SNR Threshold (dB)                               30
Client Match Load Balancing Signal Delta Bound (dB)                          5
Client Match 802.11v BSS Transition Management                               Enabled
Dynamic Bandwidth Switch                                                     Disabled
Dynamic Bandwidth Switch Wait Time (sec)                                     30
Dynamic Bandwidth Switch Triggering Indicator CCA ibss Threshold (%)         10
Dynamic Bandwidth Switch Triggering Indicator Beacon Failed Threshold        30
Dynamic Bandwidth Switch Triggering Indicator CCA intf Threshold (%)         30
Dynamic Bandwidth Switch Clear Time (min)                                    30
Client Match MU Client threshold                                             15
Client Match MU SNR threshold (dB)                                           30

show rf arm-profile default-g

Adaptive Radio Management (ARM) profile "default-g" (Predefined (changed))
--------------------------------------------------------------------------
Parameter                                                                    Value
---------                                                                    -----
Assignment                                                                   single-band
Allowed bands for 40MHz channels                                             None
80MHz support                                                                Disabled
160MHz-support                                                               None
Client Aware                                                                 Enabled
Max Tx EIRP                                                                  9 dBm
Min Tx EIRP                                                                  3 dBm
Rogue AP Aware                                                               Disabled
Scan Interval                                                                10 sec
Aggressive scanning                                                          true
Active Scan                                                                  Disabled
ARM Over the Air Updates                                                     Enabled
Scanning                                                                     Enabled
Multi Band Scan                                                              Enabled
VoIP Aware Scan                                                              Enabled
Power Save Aware Scan                                                        Disabled
Video Aware Scan                                                             Enabled
Ideal Coverage Index                                                         10
Acceptable Coverage Index                                                    4
Free Channel Index                                                           40
Interfering AP Weight                                                        25 %
Backoff Time                                                                 240 sec
Error Rate Threshold                                                         70 %
Error Rate Wait Time                                                         90 sec
Channel Quality Aware Arm                                                    Disabled
Channel Quality Threshold                                                    70 %
Channel Quality Wait Time                                                    120 sec
Minimum Scan Time                                                            8
Load aware Scan Threshold                                                    1250000 Bps
Mode Aware Arm                                                               Disabled
Scan Mode                                                                    all-reg-domain
Client Match                                                                 Enabled
Client Match Report Interval (sec)                                           30
Allows Client Match to Automatically Clear Unsteerable Clients after Ageout  Enabled
Client Match Unsteerable Client Ageout Interval                              2 Days 0 Hours
Client Match Band Steering G Max Signal (-dBm)                               45
Client Match Band Steering A Min Signal (-dBm)                               75
Client Match Sticky Client Check Interval (sec)                              3
Client Match Sticky Client SNR (dB)                                          18
Client Match SNR Delta Bound(dB)                                             10
Client Match Sticky Min Signal                                               65
Client Match Steering Timeout (sec)                                          10
Client Match Load Balancing Threshold (%)                                    20
Client Match IOS Steering Backoff Interval (sec)                             300
Client Match VBR Stale Entry Age (sec)                                       120
Client Match Max Steering Failures                                           2
Client Match Load Balancing Client Threshold                                 30
Client Match Load Balancing SNR Threshold (dB)                               30
Client Match Load Balancing Signal Delta Bound (dB)                          5
Client Match 802.11v BSS Transition Management                               Enabled
Dynamic Bandwidth Switch                                                     Disabled
Dynamic Bandwidth Switch Wait Time (sec)                                     30
Dynamic Bandwidth Switch Triggering Indicator CCA ibss Threshold (%)         10
Dynamic Bandwidth Switch Triggering Indicator Beacon Failed Threshold        30
Dynamic Bandwidth Switch Triggering Indicator CCA intf Threshold (%)         30
Dynamic Bandwidth Switch Clear Time (min)                                    30
Client Match MU Client threshold                                             15
Client Match MU SNR threshold (dB)                                           30

In your screenshot, there is an "E" after your channels which means your are using 80mhz channels.  With any type of density 80mhz channels should not be used.  You also have 42 and 34 clients on two access points which needs to be less, otherwise performance will suffer.  42 and 34 clients compete for resources, dividing performance between 42 and 34 clients.  Clients that are closer to the access point could certainly make things worse for clients that are further away.  I would take a look at the high density validated reference design guide here:  http://www.arubanetworks.com/assets/vrd/Aruba_VHD_VRD_Planning_Guide.pdf and open a TAC case to make sure you have everything configured based on your environment.  Your problems could be cause by interference, misconfiguration or a bug, but you need to take misconfiguration off the table to see if it is the other two clearly.  You can do that by opening a TAC case.