Cisco 8821 Manual page 56

802.1x, CCKM and/or PSK may also be enabled if wanting to utilize the same SSID for various type of voice clients, where
some clients do not support 802.11r (FT) depending on whether 802.1x or PSK is being utilized.
To utilize CCKM for fast secure roaming, enable WPA2 policy with AES encryption and 802.1x + CCKM for authenticated
key management type.
Cisco Wireless IP Phone 8821 and 8821-EX Wireless LAN Deployment Guide
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