VLAN Select is a feature that allows for the dynamic assignment of clients to different VLANs from a pool based on various criteria, such as load balancing or location. In a centralized wireless deployment with N+1 high availability, if clients are receiving IP addresses from a different subnet after failover despite the WLANs being configured with the same dynamic interfaces, the issue is that the second controller ' s WLAN interface mapping resolves to a different VLAN or DHCP scope. VLAN Select ensures that client VLAN assignment is consistent regardless of which controller the client connects to, preventing the subnet change behavior observed during failover. Without VLAN Select, even identically named dynamic interfaces on two WLCs may map to different VLANs if the underlying switch configuration differs. RF Protocol (Option A) controls radio parameters. AP Groups (Option B) control SSID and VLAN assignments per AP cluster. AAA Override (Option D) allows RADIUS servers to assign per-user VLANs, which requires authentication — but these SSIDs use open authentication. Reference: WLSD Study Guide — N+1 High Availability Design, VLAN Select Feature, Consistent Client VLAN Assignment Across Controllers.