Case Study: A STA Fails to Go Online Because It Fails to Negotiate with an AP Using a Cached PMK

Symptom

An Apple computer fails to connect to an AP and displays a message indicating that the key is incorrect.

Relevant Alarms and Logs

None

Cause Analysis

The STA uses the cached key to associate with the wireless network.

Procedure

1. Check the failure cause for the STA to go online. The STA fails to go online because the key is incorrect or the STA uses the cached PMK to negotiate with the AP.

   [AC-diagnose] display station online-fail-record sta-mac sta-mac
   Rf/WLAN: Radio ID/WLAN ID
   ---------------------------------------------------------------------------------------------
   STA MAC         Device type Device ID Device name  Rf/WLAN    Last record time
   Reason
   ---------------------------------------------------------------------------------------------
   yyyy-yyyy-yyyy  AP          19        18F-AP02     2/1        2021-03-05/17:41:56
   The key is incorrect or the STA uses the cached PMK.
   ---------------------------------------------------------------------------------------------

2. Check the STA online process using the station-trace function. It is found that the STA used the cached PMK to negotiate with the AP. As a result, the STA failed to go online.

   [AC-diagnose] station-trace sta-mac sta-mac
   The following error information is displayed:
   <7>Mar 05 2021 18:06:10.270.1 AP01 WIFI/7/BTRACE:[BTRACE][WLAN_WIFI][yyyy-yyyy-yyyy]:SeqNo[4264] [EAPOL] EAPOL key handshake 1/4 payload[117] Recved from software switch
   <7>Mar 05 2021 18:06:10.270.2 AP01 WIFI/7/BTRACE:[BTRACE][WLAN_WIFI][yyyy-yyyy-yyyy]:SeqNo[4264] [EAPOL] EAPOL key handshake 1/4 payload[117] elapsed[0 ms] Sending pkt to target(Single)
   <7>Mar 05 2021 18:06:10.270.3 AP01 WIFI/7/BTRACE:[BTRACE][WLAN_WIFI][yyyy-yyyy-yyyy]:SeqNo[4264] [EAPOL] EAPOL key handshake 1/4 payload[117] elapsed[0 ms] Success to send pkt to air
   <7>Mar 05 2021 18:06:10.270.4 AP01 WIFI/7/BTRACE:[BTRACE][WLAN_WIFI][yyyy-yyyy-yyyy]:SeqNo[4265] [EAPOL] EAPOL key handshake 2/4 payload[117] Recved from target
   <7>Mar 05 2021 18:06:10.270.5 AP01 WIFI/7/BTRACE:[BTRACE][WLAN_WIFI][yyyy-yyyy-yyyy]:SeqNo[4265] [EAPOL] EAPOL key handshake 2/4 payload[117] elapsed[0 ms] Entering rx reorder
   <7>Mar 05 2021 18:06:10.270.6 AP01 WIFI/7/BTRACE:[BTRACE][WLAN_WIFI][yyyy-yyyy-yyyy]:SeqNo[4265] [EAPOL] EAPOL key handshake 2/4 payload[117] elapsed[0 ms] Exiting rx reorder for release
   <7>Mar 05 2021 18:06:10.270.7 AP01 WIFI/7/BTRACE:[BTRACE][WLAN_WIFI][yyyy-yyyy-yyyy]:SeqNo[4265] [EAPOL] EAPOL key handshake 2/4 payload[117] elapsed[0 ms] Success to send pkt to software switch
   <7>Mar 05 2021 18:06:10.270.8 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):receive eap pkt from sta by BSS(37),[type(3)=EAPoL-Key, destmac=dc:21:e2:ad:ba:e0, len=139]
   <7>Mar 05 2021 18:06:10.270.9 AP01  WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):[WPA] Receive eapol-key message.
   <7>Mar 05 2021 18:06:10.270.10 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):[WPA] MIC is wrong. It will try to retransfer msg1/4. AuthType = 6 & Retransfer-Num = 0
   <7>Mar 05 2021 18:06:10.270.11 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):[WPA] EAPOL-Key (message2/4) packet's MIC is wrong
   <7>Mar 05 2021 18:06:10.270.12 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):[WPA] Notice MIC check faild.
   <7>Mar 05 2021 18:06:10.270.13 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):server : notify handshake result :
   IsPtkRekey                  = 0
   keyBitMap(0x1:ptk,0x2:gtk)  = 0x1
   result(0:success,1:fail)    = 2
   <7>Mar 05 2021 18:06:10.270.14 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):AC delete the station:
   radio id :1
   wlan id  :1
   op type  :The WMP deletes the STA[5]
   <7>Mar 05 2021 18:06:10.290.1 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):Del 11R sta
   <7>Mar 05 2021 18:06:10.290.2 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):[WPA] SAE notify Del sta (R:1, V:17) Ret:185008129
   <7>Mar 05 2021 18:06:10.290.3 AP01 WSRV/7/BTRACE:(BTRACE)(WLAN_AP)(yyyy-yyyy-yyyy):WUAMK_AssocreqCallChainHandle[966]: Enter:
   radio id    :1
   wlan id     :0
   packet type :disassociation
   result      :0
   reason      :The WMP deletes the STA (0x2000005)
   sta ability :0
   SFN roam    :0
   SNR         :37

3. Clear the connection records on the PC, search for and associate with the wireless network again, and enter the password. Then, the Apple computer connects to the network successfully.