The scenario describes a classic FlexConnect configuration issue. When an AP is in FlexConnect mode and a WLAN is configured for local switching, the AP must know which VLAN to place client traffic on at the remote site. This is accomplished by creating a FlexConnect group on the WLC, adding the APs to this group, and then defining a specific WLAN-to-VLAN mapping within the group's configuration. The failure of WLAN B in FlexConnect mode indicates it is configured for local switching but lacks this required VLAN mapping. Creating a FlexConnect group with the proper mapping will provide this information to the APs, allowing WLAN B to function correctly.

B. Disable local switching on the WLANs: This is a design change, not a configuration fix. It would force all traffic centrally, which may not meet the network requirements and doesn't correct the underlying local switching misconfiguration.

C. Map the AP group to the WLAN interface: This describes a non-existent configuration step. AP groups determine which WLANs are broadcast by APs, while WLANs are mapped to interfaces on the WLC for central switching.

D. Join the APs to a Cisco FlexConnect group: This action is incomplete. Simply joining a group is insufficient if the group has not been configured with the necessary WLAN-VLAN mappings, which is the crucial step described in option A.

1. Cisco Wireless Controller Configuration Guide

Release 8.5

"FlexConnect" Chapter

"Configuring FlexConnect Groups" section: "You can use FlexConnect groups to push the VLAN-specific configurations on the FlexConnect APs... You can create a FlexConnect group and assign a specific AP to the FlexConnect group. The APs in the group will inherit the VLAN and ACL configurations of the FlexConnect group." This document explicitly states that FlexConnect groups are used to configure VLANs for APs.

2. FlexConnect Configuration Guide

Cisco IOS XE Gibraltar 16.12.x

"Configuring FlexConnect Groups" section: "You can use FlexConnect groups to do the following: ... Efficiently configure WLAN-VLAN mapping for a group of FlexConnect APs." This confirms that the primary method for assigning VLANs to WLANs in a FlexConnect deployment is through FlexConnect groups.

3. Cisco Catalyst 9800 Series Wireless Controller Configuration Guide

IOS XE Dublin 17.12.x

"Configure FlexConnect" Chapter

"WLAN-VLAN Mapping" section: "For locally switched WLANs

traffic from the clients is switched to a local VLAN at the AP's location... To configure VLANs on FlexConnect APs

you must configure FlexConnect Groups." This directly links the requirement for VLANs in local switching to the configuration of FlexConnect Groups.