How to configure WLAN Controller failover for Lightweight Access Points

Consider a scenario where there are two Wireless LAN Controllers (WLCs) named WLC1 and WLC2. These WLCs are configured in the same subnet in one WLAN. In order to achieve high availability, this is how the WLAN is configured:

1. WLC1 and WLC2 are configured within the same mobility group.
   
   
   
2. Half of the access points are configured to use WLC1 as the primary WLC and use WLC2 as the secondary WLC.
   
   
   
3. The other half of the access points are configured to use WLC2 as the primary WLC and use WLC1 as the secondary WLC.
   
   
   
4. The fallback feature is enabled on both WLC1 and WLC2.

If any of the WLCs go down, the access point that is joined to the failed WLC  recognizes this (keep alive (heartbeat) between access point and WLC). Therefore, the access point begins to join the good WLC, which still runs. This is not stateful failover, which means that the access point has to join the new WLC and therefore the wireless clients.

Also, if either of the WLCs do not work and the affected access points re-register to the other WLC, then the wireless clients have to re-associate and therefore lose wireless connection during failover as it is not stateful failover. The failover is not transparent to the WLAN client. That is, the WLAN clients lose their WLAN connectivity during access point failover.

Access points and clients are not effected on the WLC that runs. This means that the fallback of the access point is not transparent to the clients. Only access points and clients on the failed WLC are effected.

In order to configure the WLAN Controller failover for Lightweight Access points, the Access Point must be configured correctly in a mobility group for the AP failover and each Wireless LAN Controller (WLC) must have the AP failover feature enabled.

Refer to these documents for more information:

• WLAN Controller Failover for Lightweight Access Points Configuration Example
  
  
  
• Wireless LAN Controller (WLC) Troubleshoot FAQ.

For more information on configuring load balancing in WLC, refer to TAC case K34115297