Case Study: Two STAs Connected to the Same SSID on the Same AP Cannot Communicate with Each Other Because the traffic-optimize bcmc deny all Command Is Executed on the Device

Symptom

In tunnel forwarding mode, two STAs connected to the same SSID on the same AP cannot communicate with each other.

Relevant Alarms and Logs

None

Cause Analysis

The traffic-optimize bcmc deny all command is configured on the device, which restricts ARP packet forwarding.

Procedure

1. Run the display traffic-profile command on the AC. The user isolation and traffic filtering policies are not configured in the traffic profile.
2. Use the station-trace function to check the ICMP and ARP packet exchange process of the STA.
   1. Ping STA2 from STA1 and run the station-trace sta-mac sta1-mac command. ARP request packets are sent but no response is received.
   2. Ping STA1 from STA2 and run the station-trace sta-mac sta2-mac command. No ARP request packets are sent.

3. Display the forwarding process of ARP request packets through debugging to locate the fault.

   <AP> terminal monitor
   <AP> terminal debugging
   [AP-diagnose] debug cap print condition arp arp-request
   [AP-diagnose] debug cap print condition arp target-ip B-ip-address
   [AP-diagnose] debug cap print on print-num 2
   [AP-diagnose]
   Jul 08 2021 13:04:55.360.2+08:00 W-B1F-NW
   MFPI/7/DEBUG:18][cycle:11590138898995][msec:482922454]
   [FastFlag:0][NPFastFlag:0][FirstIf:15][CurRxIf:15][CurTxIf:15][RxTop:1][TxTop:1][TraceFlag:0][TraceInstanceId:0]
   
   SVC Egress Unicast PktType:1, PBUF_GET_CAP_PKT_ALL_BCMC_DENY_FLAG[0]
   Packet data:
   ffffffff ffffd0ab d5b13384 81000021
   08060001 08000604 0001d0ab d5b13384
   c0a82196 00000000 0000c0a8 217b

4. According to the preceding debugging information, the bcmc policy is configured in the traffic profile, causing the communication failure between the STAs. Run the undo traffic-optimize bcmc deny all command in the traffic profile to delete the configuration. The fault is rectified.