A failed VLAN Probe indicates that the gateway cluster members do not have the required common Layer 2 connectivity for those VLANs. When the VLAN probes fail, the relationship between cluster members is effectively treated as L3-connected rather than L2-connected. Aruba’s clustering documentation distinguishes these two operating conditions very clearly.

For an L3-connected cluster, only APs are fully replicated. Client/user information is not fully synchronized between cluster members, and high-value application sessions are not synchronized. Aruba’s official ArubaOS 8 Fundamentals Guide summarizes the distinction as follows: for L2-connected members, APs and clients are fully replicated, users and high-value sessions are synchronized, and failover occurs without deauthentication. For L3-connected members, only APs are fully replicated, users and high-value sessions are not synchronized, and users can be deauthenticated during failover. Aruba Networks

Therefore, option B precisely describes the outcome when VLAN probing fails across the required VLANs. Option A requires L2-connected clustering. Option C describes full L2 redundancy. Option D is reversed: L3-connected operation does not provide hitless client failover and users may be deauthenticated during a gateway failure. Aruba Networking

Study Guide Topics: Gateway Clustering, VLAN Probe, L2-Connected vs. L3-Connected Clusters, AP/Client State Synchronization, Stateful Failover, High-Value Session Synchronization.