To enable Juniper Mist Access Assurance for 802.1X (RADIUS) authentication with Cisco APs, the correct approach is to configure a new 802.1X SSID on the Cisco AP referencing your Juniper Mist Edge as the RADIUS server (option C). According to Juniper Mist’s official documentation and architecture guides: “Mist Access Assurance supports end-client authentication on third-party infrastructure by leveraging the Mist Auth Proxy application running on a Mist Edge platform. Third-party devices, such as Cisco APs, are added as RADIUS clients at Mist Edge. The Mist Edge proxy handles all RADIUS authentication traffic from the APs, wraps these authentication requests into a secure RadSec tunnel, and relays them to the Mist Access Assurance cloud for validation against configured authentication rules.”

This deployment does not require direct RADSEC tunneling from Cisco APs to Mist Access Assurance (since Cisco APs are not natively RADSEC capable) but uses Mist Edge as an intermediary RADIUS server and authentication proxy. "Add an authentication rule in Access Assurance to permit user access," enabling centralized management and policy enforcement in the Mist Cloud.