Comprehensive and Detailed Explanation From Exact Extract of HPE Aruba Networking Switching:

In AOS-10 wireless deployments, HPE Aruba Networking supports the configuration of Primary and Secondary Gateway Clusters in the SSID profile to ensure high availability, redundancy, and load distribution. This configuration follows Aruba’s gateway clustering best practices, where access points (APs) attempt to establish tunnels with their Primary Gateway Cluster first. If the AP cannot reach the primary cluster (due to reachability, latency, or network topology), it automatically connects to the Secondary Gateway Cluster.

When both gateway clusters are active and reachable but some APs cannot reach the primary cluster—for example, due to Layer 3 routing, firewall restrictions, or network segmentation—those APs will associate with the secondary cluster instead. This results in an approximately equal split of APs across both clusters, even though the primary cluster is operational.

Exact Extract from HPE Aruba Networking Switching and AOS-10 Gateway Documentation:

“Access Points attempt to form tunnels with the Primary Gateway Cluster first. If the primary cluster is unreachable or fails to respond within the defined timeout, the AP establishes a tunnel with the Secondary Gateway Cluster.”

“When the primary and secondary gateway clusters are both up but APs are distributed across separate routed networks or VLANs, APs may select the gateway cluster that is most reachable at that time, resulting in an even or partial split of AP distribution.”

“This is expected behavior when APs in different subnets cannot reach the same primary cluster due to network topology. The secondary cluster provides redundancy and connectivity continuity.”

Therefore, the equal split of 260 APs is explained by the fact that while the primary cluster is active, a subset of APs cannot reach it due to routing or segmentation and thus join the secondary cluster—this behavior aligns with Aruba’s gateway redundancy mechanism.

Why the Other Options Are Incorrect:

A. The statement reverses the cause: APs that cannot reach the primary connect to the secondary—not the other way around. The secondary cluster’s reachability does not affect AP selection when the primary is available and reachable.

“APs first attempt the primary cluster; only failure to reach it triggers fallback to secondary.”

B. Secondary cluster is homogeneous:Cluster homogeneity refers to identical hardware/software versions between gateways; it does not influence AP distribution or equal load split.

“Homogeneity is a software version consideration, not an AP load-balancing factor.”

C. Secondary cluster is heterogeneous:Heterogeneity (mixed hardware types) is unsupported or discouraged; it does not cause AP distribution behavior.

“Heterogeneous gateway clusters are not a cause of AP distribution variation; cluster type does not dictate AP split.”

References of HPE Aruba Networking Switching Documents or Study Guide:

ArubaOS 10 Gateway and AP Deployment Guide – “Primary and Secondary Gateway Cluster Configuration and AP Association Logic.”

Aruba High Availability and Clustering Best Practices Guide – “Gateway Cluster Failover, Redundancy, and AP Selection.”

Aruba Central Cloud Management and Monitoring Guide – “SSID Profile Configuration: Primary and Secondary Gateway Clusters.”

Aruba Campus Wireless Design Guide (AOS 10.x) – “Cluster Reachability, Redundancy, and Role Propagation Across Gateways.”