WLC AP Fallback Design for N+1 Redundancy
A customer has multiple WLCs running in N+1 redundancy with APs load balanced between the WLCs. The customer performs AP failover testing between the WLCs and notices that some of the APs do not move back to their primary WLC after it recovers. What are two points that must be addressed in the design? (Choose two.)
Community Votes
100% of anonymous learners picked answer DE. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
The exam tests the specific mechanism of AP reassociation, highlighting the common trap of assuming APs automatically roam back; in reality, explicit configuration of AP Fallback and accurate Primary WLC settings are required.
This question addresses the design requirements for ensuring Access Points return to their primary Wireless LAN Controller after a failover event in an N+1 redundancy architecture. It establishes that both the fallback feature and correct primary controller configuration are essential for proper behavior.
Many learners incorrectly select options related to DHCP Option 43 or Secondary WLC configuration, confusing initial discovery/joining mechanics with post-failover recovery logic.
Community Discussion (5 comments)
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Expert Analysis
Why the Answer Is Correct
AP Fallback is a feature that allows an AP to leave its current active controller and return to its preferred primary controller once it becomes available again. Without this feature explicitly enabled on the controllers, APs may remain associated with the secondary (backup) controller indefinitely. Furthermore, for the AP to successfully reconnect to the primary controller, the primary controller's information must be correctly configured in the AP's settings (or via DHCP/Proxy DHCP). If the primary WLC information is incorrect, the AP cannot identify or reach its home controller even if fallback is enabled.Why the Other Options Are Wrong
DHCP Option 43 is used for initial controller discovery during boot-up, not for managing reassociation after a failure has occurred. Similarly, while the secondary WLC must be reachable for the failover itself, the issue described is about returning to the primary, not joining the secondary. Setting priorities to 'Low' might affect which controller is chosen first but does not prevent the return process if fallback is enabled. The core issue is the lack of a directed path back to the primary.Community Comment Notes
Community consensus strongly supports options D and E. As Jonycici noted, "If AP Fallback is not enabled... only the APs connected to WLCs with this feature enabled will return." This confirms that fallback is the enabling mechanism. Another commenter reinforced that "DE are the right choices," aligning with the official understanding that both the feature toggle and the target address (Primary WLC info) are necessary conditions.Exam Strategy
When designing high-availability wireless networks, always verify that 'AP Fallback' is enabled if you require deterministic placement of APs on their primary controllers. Remember that failover is one-way by default; returning requires explicit configuration of both the action (fallback) and the destination (primary IP/DNS).
Frequently Asked Questions
Does AP Fallback happen automatically without configuration?
No, AP Fallback is a feature that must be explicitly enabled on the Wireless LAN Controllers. If disabled, APs will stay on the backup controller.
Why isn't Secondary WLC configuration the issue here?
Secondary WLC config ensures the AP can join during a failure. The problem is returning to the primary, which depends on Fallback being enabled and Primary info being correct.