Case Study: STA 802.1X Authentication Fails Due to Insufficient AP Signal Coverage

Symptom

802.1X authentication is configured on an AC. After a STA associates with an AP, 802.1X authentication fails.

Relevant Alarms and Logs

None

Cause Analysis

The wireless signal coverage is insufficient. As a result, the signal from the terminal location to the AP is weak, affecting authentication and access.

Procedure

1. Reproduce the fault and use the trace and station-trace functions to check the authentication packet exchange process.

   [AC] trace object mac-address sta-mac
   [AC] trace enable
   [AC-diagnose] station-trace sta-mac sta-mac

   The command output shows that the signal strength received by the STA is -79 dBm and the STA does not respond to the Request Challenge packet. Therefore, the STA may fail to be authenticated due to a packet exchange failure caused by weak signal strength.

   [BTRACE][2020/05/28 16:40:04][13824][WLAN_AC][sta-mac]:[Process:54] [WSTA] Receive STA (Re)associate request message.
   Assoc local:0, AP ID:933, Radio ID:1, Wlan ID:2, Type(1:assoc, 2:reassoc):1,...., Rssi:-79,
   [BTRACE][2020/05/28 16:40:14][13824][EAPoL][sta-mac]:  Resend a EAPoL request challenge packet to user.
   [BTRACE][2020/05/28 16:40:14][13824][EAPoL][sta-mac]:  Add a Eap Packet Node to EAPOL Ucib, MAC is x-x-x.
   [BTRACE][2020/05/28 16:40:14][13824][EAPoL][sta-mac]:  EAPOL packet: OUT
   [BTRACE][2020/05/28 16:40:14][13824][EAPoL][sta-mac]:  802.1x packet:
   Version:802.1X-2001(1); Type:Eap(0); Length:788
   EAPOL packet:
   Code:Request(1); Id:129; Length:788; Type:PEAP(25)
   [BTRACE][2020/05/28 16:40:12][13824][EAPoL][sta-mac]: Send EAP_request packet to user successfully.(Index=9052)
   [BTRACE][2020/05/28 16:40:14][13824][EAPoL][sta-mac]: No response of request challenge from user.

2. Move the STA close to the AP and perform the test again. The authentication is successful. It is confirmed that the authentication fails because the AP signal coverage is insufficient and the signal strength is weak.
3. After the AP coverage is enhanced, the problem is solved.

Suggestion and Summary

Proper signal coverage is the basis for STAs to use a wireless network. Insufficient signal coverage affects STA access and authentication. Similarly, if a signal coverage overlap range is large, an authentication exception may also be caused due to a left-right connection problem in an authentication process of the STA.