Refer to the exhibit. A network engineer has identified that during a recent controller failure, several access points failed over to the tertiary controller instead of the secondary controller…

While a secondary controller being at capacity could prevent APs from joining it, the question implies a preference or re-ordering during failover rather than a capacity constraint.

An HA-SKU controller typically refers to a High Availability setup (like N+1 or SSO), but its SKU alone does not inherently grant it priority over a configured secondary controller in a standard failover list.

If the secondary controller is part of an SSO configuration, it would typically act as a hot-standby unit for another controller, effectively functioning as a single logical entity rather than a separate tertiary failover option.

Access points often prioritize Wireless LAN Controllers (WLCs) that are discovered via Layer 2 (broadcasts) or that are in the same IP subnet as their current primary controller during failover. If the tertiary controller resides in the same subnet as the failed primary, and the secondary controller is in a different subnet, the AP may find and connect to the tertiary controller first due to local subnet proximity and discovery mechanisms, even if the secondary is explicitly listed in its configuration.