Access Points are not forming backup tunnel in HA pair
Some APs are not forming backup tunnel in HA pair
WLAN services fail to sync
High Availability (HA) / Failover
Firmware 9.21.x, 10.x
The tunnel between AP and secondary controller may not establish if the secondary controller does not meet the AP capacity of the primary controller. This may be due to a misconfiguration of the VMware CPU and RAM settings which determine the size (small / medium / large) of an elastic controller. Synchronization between controllers may also fail in this scenario.
Make sure both controllers are configured as the same size (small / medium / large).