C9120AX-C Not able to join 9800 WLC

[Chrioni Siakla]

C9120AX-C was previously joined to the controller, but for some reason it stopped working. Upon checking it disappeared from the controller. The last join attempt stats below

[Leo Laohoo]

What firmware is the WLC on? 

What is date of manufacture of the AP?

[Chrioni Siakla]

Hi Leo AP image version 17.9.3.50  Controller 17.9.3.50

[Leo Laohoo]

Factory-reset the AP, plug a console cable into the AP and reboot the AP. 

Dump the boot-up process.

[Chrioni Siakla]

attached logs when I restarted capwap for the AP

[Leo Laohoo]

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@Chrioni Siakla wrote:

Dec 28 02:10:37 kernel: [*12/28/2023 12:10:37.0011] AP has joined controller WLC

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It says the AP has successfully joined the controller.

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@Chrioni Siakla wrote:

Dec 28 02:10:53 kernel: [*12/28/2023 12:10:53.9882] Max retransmission count exceeded, going back to DISCOVER mode.

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However, 16 seconds later, the AP drops out. 

Please describe the network?  Start with the description of the network where the AP is connected to?

[Chrioni Siakla]

have factory reset and same result

[Scott Fella]

It’s easy if you take a look at this guide and other guides about AP troubleshooting. Also, if you console into the ap and reboot it, that usually will provide information on what is happening. 
https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/218396-troubleshoot-catalyst-9800-ap-join-or-di.html

[Rich R]

Upgrade the WLC as per the TAC recommended link below.  Currently: Cisco recommends 17.9.4 + SMU_CSCwh87343 + APSP (as needed) OR 17.9.4a + APSP(as needed) for all deployments.

Make sure you install the latest SMUs and APSP.

[Chrioni Siakla · Accepted solution]

We've fixed this issue upgrading from 17.9.3.50 to 17.9.4a (Cisco recommend at this as a stable version ).

[Samuele Leardini]

Hi Chrioni, when you had the AP join issue, were your APs on Local mode or Flexconnect mode?

Thanks
Samuele

[Chrioni Siakla]

few of the C9120AX-C previously joined and working then cant join the WLC anymore, I am still able to SSH into the WAPs

[Rich R]

You might want to try 17.9.5 which was released last week - it includes fixes for both these bugs which might be related to your issue:

CSCwh61011

Cisco Catalyst 9120 and 9115 APs unexpectedly disjoins from the controller and does not establish DTLS again.

CSCwi04855

APs disjoin from the controller repeatedly with traceback logs.

[Leo Laohoo]

CSCwi88967 (AP9120 randomly disconnecting from the WLC running S/W version 17.9.5.42) is a bit "confusing".  Title says 17.9.5 but Known Affected Version says 17.9.4.