C9115 joins C9800 and then drops and repeats.

[CCC3]

I'm trying to join C9115 to C9800, but it repeats joins and drops.
Looking at show logging in ap,

kernel: [*02/21/2023 12:42:21.8250] Re-Tx Count=1, Max Re-Tx Value=5, SendSeqNum=34, NumofPendingMsgs=3
kernel: [*02/21/2023 12:42:21.8250]
kernel: [*02/21/2023 12:42:24.6750] Re-Tx Count=2, Max Re-Tx Value=5, SendSeqNum=35, NumofPendingMsgs=4
kernel: [*02/21/2023 12:42:24.6750]
kernel: [*02/21/2023 12:42:27.5260] Re-Tx Count=3, Max Re-Tx Value=5, SendSeqNum=35, NumofPendingMsgs=4
kernel: [*02/21/2023 12:42:27.5260]
kernel: [*02/21/2023 12:42:30.3770] Re-Tx Count=4, Max Re-Tx Value=5, SendSeqNum=36, NumofPendingMsgs=5
kernel: [*02/21/2023 12:42:30.3770]
kernel: [*02/21/2023 12:42:33.2280] Re-Tx Count=5, Max Re-Tx Value=5, SendSeqNum=37, NumofPendingMsgs=6
kernel: [*02/21/2023 12:42:33.2280]
kernel: [*02/21/2023 12:42:36.0790] Max retransmission count exceeded, going back to DISCOVER mode.

After it appeared like this, I confirmed it was falling off the C9800.

Note that ntp is not used.
The time with WLC and AP is the same.

[Kasun Bandara]

at first check 2 things. 

1. time of AP and WLC

2. regulatory domain match

[CCC3]

Thanks.

Times are the same as for other APs.

How are regulatory domains checked?

[Kasun Bandara]

@CCC3 check APs full model number C9115AXI-x (simple X is the regulatory domain) check if that is allowed in WLC settings.

https://www.cisco.com/c/dam/assets/prod/wireless/wireless-compliance-tool/index.html use this tool to find exact country to configure in WLC

[marce1000]

 - Use the following commands on the 9800 to troubleshoot :
                   show logging  profile wireless filter mac <ap radio mac>
                   show logging profile wireless filter mac <ap radio mac> trace-on-failure
                   show wireless stats trace-on-failure

  Also  review the C9800   configuration with the CLI command : show  tech   wireless , have the output analyzed by  https://cway.cisco.com/tools/WirelessAnalyzer/  , please note do not use classical show tech-support (short version) , use the command denoted in green for Wireless Analyzer.               Checkout all advisories!

 M.                   
                   
           

[Rich R]

And instead of just a snippet from the AP log - the complete AP log from power-on.
What model of 9800?
What version of IOS-XE?
Have you checked all the field notices below?

[Leo Laohoo]

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@CCC3 wrote:
After it appeared like this, I confirmed it was falling off the C9800.

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Field Notice: FN - 72278 - Some C9120 and C9115 APs Stuck in Bootup with 'Uncorrectable ECC Error' Displayed