Recommended configuration for WLAN-VLAN mapping
When configuring Cisco WLC WLANs, there are three WLAN-VLAN mapping options.
The difference between AP-Specific and the other two WLAN-VLAN mappings is that the AP-Specific configuration is saved in the AP’s flash memory. Group-Specific and Wlan-Specific are saved in the WLC. Whenever an AP joins the WLC, it will download the configuration from the WLC, and there will be WLAN-VLAN mapping information.
This difference leads to the instability of AP-Specific. For example, when an AP joins another WLC and joins back, the AP-Specific configuration will be lost. Referring to the official documentation, Cisco’s recommended configuration is FlexConnect group (Group-Specific).
In case of FlexConnect VLAN mapping deployment, we recommend that the deployment be done using FlexConnect groups. This allows you to recover VLAN mapping after an AP rejoins the Cisco WLC without having to manually reassign the VLAN mappings.https://www.cisco.com/c/en/us/td/docs/wireless/controller/release/notes/crn83mr5.html