Dual-Link Switchover or Revertive Switching Fails

Symptom

In a dual-link backup scenario, an active/standby AC switchover or revertive switching fails.

Possible Causes

• The active AC is faulty.
• The faulty active AC recovers.
• A switchover occurs due to the change in the priorities of the active and standby ACs.
• A switchover occurs due to the change in the IP addresses of the active and standby ACs.

Procedure

1. Check whether the link to the active AC is faulty.
   When the active AC fails or the link between the AC and AP fails, services are switched between links.

   1. Check whether the AC is faulty and cannot be accessed.
   2. Perform the ping operation to check whether the link between the AC and AP works properly.

      If the ping operation fails, the link between the AC and AP is not connected.

      Run the ping command to check the test result.

      <AC> ping 10.1.15.252
        PING 10.1.15.252: 56  data bytes, press CTRL_C to break
          Request time out 
          Request time out 
          Request time out 
          Request time out 
          Request time out 
        
        --- 10.1.15.252 ping statistics ---  
          5 packet(s) transmitted  
          0 packet(s) received 
          100.00% packet loss 

2. Check whether the faulty active AC recovers.
   This is a normal situation where services are switched back to the recovered active AC.

   1. Check the onsite environment to check whether the faulty active AC recovers.

      Determine whether the AC fails and recovers based on information collected onsite.

   2. If the AC recovers, log in the AC to check the IP address of the standby AC. If an IP address is configured and is the same as the IP address of the AC where the switchover occurs, the recovered AC is the active AC. The specified priority configuration in the AP system profile takes precedence over the global configuration on the AC.

      Run the display ac protect command to check the dual-link backup status, AC switchback status, AC priority, and standby AC's IP address in the WLAN view.

      [AC20] display ac protect 
      ------------------------------------------------------------ 
      Protect state             : disable 
      Protect AC                : - 
      Priority                  : 0 
      Protect restore           : enable 
      Coldbackup kickoff station: disable
      ------------------------------------------------------------ 

      Run the display ap-system-profile name profile-name command to check the AC priority and the standby AC's IP address in the AP system profile view.

      [AC20] display ap-system-profile name default
      ------------------------------------------------------------------------------ 
      AC priority                   : -
      Protect AC IP address         : -
      AP management VLAN            : -
      Keep service                  : disable 
      Keep service allow new access : disable 
      Temporary management switch   : disable 

3. Check whether the active and standby ACs have the same priority.

   If the active and standby ACs have the same priority, the AP switches to the AC with a smaller IP address.

   For details on how to check the AC's priority, see 2.

   Run the display capwap configuration command to check the IP address of the AC. If an IP address is configured as the source IP address is an IP address, the IP address is directly displayed. If a VLANIF address is configured as the source interface, the IP address of the VLANIF address is displayed.

   [AC20] display capwap configuration
     ------------------------------------------------------------ 
     Source interface                            : - 
     Source ip-address                           : 10.1.1.111 
     Echo interval(seconds)                      : 25
     Echo times                                  : 6
     Control priority(server to client)          : 7
     Control priority(client to server)          : 7
     Control-link DTLS encrypt                   : disable
     DTLS PSK value                              : ******
     PSK mandatroy match switch                  : enable
     Control-link inter-controller DTLS encrypt  : disable
     Inter-controller DTLS PSK value             : ******
     IPv6 status                                 : disable 
     ------------------------------------------------------------

4. Check whether the active and standby ACs start successively and have different priorities.
   If the standby AC starts later and has a higher priority than the active AC, a link switchover is triggered.

   1. Check whether the standby AC starts later and has a higher priority than the active AC.
      • Check the device running time to determine whether the standby AC starts later.
      • For details on how to check the AC's priority, see 2.
   2. If the standby AC starts later than the active AC but two ACs have the same priority, go to 5.

5. Check whether the active and standby ACs start successively and have the same priority.
   If the standby AC starts later, has the same priority as the active AC, but has a smaller IP address, a link switchover is triggered.

   1. Check whether the standby AC starts later but has the same priority as the active AC.
      • Check the device running time to determine whether the standby AC starts later.

        For details on how to check the AC's priority, see 2.

   2. If the active and standby ACs have the same priority, check whether the active AC has a smaller IP address. If the IP address of the active AC is larger than the IP address of the standby AC, go to 6.

6. Collect related information and contact technical support personnel.

   Run the following commands to collect device information.

   Command	Function
   <AC> save logfile	Saves diagnostic logs.
   [AC-diagnose] info-center create logbook xx.xml	Creates a dictionary file of diagnostic logs.

   Access the logfile folder and export log.log, log.dblg, and created dictionary file xx.xml.