Fault Case: In a Dual-Link Scenario, an Active/Standby AC Switchover Occurs and a Revertive Switchover Is Performed. Before the Revertive Switchover, the AP Restarts. After the AP Goes Online Again, an Incorrect Active/Standby AC Is Selected

Symptom

In a dual-link scenario, an active/standby switchover occurs on an AP. Before the revertive switchover, the AP restarts. After the AP goes online, it selects an incorrect active/standby AC. (After the restart, the AP selects the original standby AC as the active AC.)

Relevant Alarms and Logs

None

Cause Analysis

Before the revertive switchover, the AP status on the active AC is standby and the AP status on the standby AC is normal. Therefore, the restart command can be delivered only on the standby AC.

When the AP restarts, the link status of the AP in standby state is not deleted from the active AC (the active AC needs to detect that the AP does not receive echo heartbeat packets within three echo intervals). As a result, the number of connected APs in the discover response packet sent by the active AC after the AP restarts is greater than that on the standby AC, therefore, after the AP restarts, it goes online on the standby AC.

Procedure

1. Check whether the dual-link backup function is enabled on the active AC.

   The check result shows that the dual-link switch is enabled.

2. Check whether the IP address of the standby AC is configured on the active AC.

   The IP address of the standby AC has been configured.

3. Analyze the load on the active and standby ACs.

   The number of APs that can be connected to the active AC is smaller than the number of APs that can be connected to the standby AC. Therefore, the APs restart and go online on the standby AC.

Suggestion and Summary

In the dual-link scenario, it takes three echo periods to detect that the AP does not receive echo heartbeat packets. Then, the AP considers that the AP is faulty and deletes the link entry. Therefore, this problem occurs when the AP is restarted on the standby AC before the link switchback after the active AC recovers.