Unable to join cell phones to specific APs in an environment

[remacamelo]

Hello All,

I have an environment with 4 Access Points model C9120AXI-A registered in a Cisco Catalyst 9800-CL Wireless Controller firmware 17.12.3 and these APs are with software version 17.12.3.31. For these APs I disabled the frequency 2.4Ghz keeping only 5Ghz working. For my surprise The computers\laptops are able to connect normally but mobile phones are able to connect only in 2APs, in the other two the cell phones can't even see the SSID for connection. When I enable the 2.4Ghz frequency in thse APs the mobile phones works fine.

Can anyone help me solve this problem?

Thank you.

[balaji.bandi]

So you mean to say all the Phones able to connect to that 2 AP's ?

or the phones not working does not connect to any AP's  ?

Looks for me the phones might have old chipset, check the Phone mode and support ? try upgrading to latest code on the Phones and test.

by the way what Phones they are  ? (model and code running on it /)

[MHM Cisco World]

Phone NIC is support only 2.4 GHz 

It not issue of AP nor WLC it issue of phone NIC

MHM

[Mark Elsen]

  @remacamelo   That's a client issue : troubleshoot with instructions from
  : https://logadvisor.cisco.com/logadvisor/wireless/9800/9800ClientConnectivity
                           These results , so RadioActive traces can be analyzed with : 

                                                   Wireless Debug Analyzer

  M.

[Stefan Mihajlov]

@remacamelo 

I had a similar issue when I was setting up Cisco Spaces — in my case it turned out to be an RF problem (channels/power). Once I adjusted the RF settings the phones started seeing the SSID normally, so I’d suggest checking the RF profile and channel assignment on those APs as well.

[Rich R]

For everybody blaming the phones - they can connect to 2 of the APs but not the other 2 - that points to an AP problem not a phone problem!

@remacamelo 17.12 has a number of bugs which can cause the radios to stop working.
Usually reloading the AP will temporarily fix the problem so you can try that as an initial test.
But what you really need to do is upgrade to 17.12.5 with APSP6 to make sure you have all the additional fixes.

Now there is another bug affecting 17.12 but which has only been fixed in 17.15 so far:
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwp07242
It's logged for 9105 but due to common Broadcom code it should also affect 9120 (and you can see 9105/9115/9120 listed in Affected Products).
So you may also want to consider upgrading to 17.15.4b to get that fix.

[remacamelo · Accepted solution]

Hello All,

  Sorry the delay to reply here. I was planning to upgrade the firmware version according @Rich R suggestion but before it I decided to perform a factory reset in these APs and after this procedure the cell phones are connecting normally in the APs. 

Thank you all for the help.

[Rich R · Accepted solution]

Good to hear @remacamelo but are you sure it was the factory default reset that did it or just the AP reload?

If the problem returns that will confirm it was just the reload that cured it temporarily.  Then I suggest 17.15.4b will be your next step.