Using the Centrify platform, you can configure multi-factor authentication (MFA) for VPN connections. The configuration requires calling an API to invoke a specific MFA policy defined in Access > Policies > Third Party Integration.
See On Demand Challenge API for details on the API.
For information about using a RADIUS server here, you can configure the connector to act as a RADIUS server. For details, see Configuring the Centrify Connector for use as a RADIUS server.