Since RAS v18 this is now possible to specify two RADIUS hosts to provide high availability and failover.
1. In Parallels RAS Console go to > Connection > Multi-factor Authentication tab.
2. Choose the needful RADIUS provider (e.g. DUO), specify primary and secondary RADIUS servers and High Availability mode:
The following High Availability modes are available:
- Active-active (parallel) - upon authentication attempt, the request is sent to both RADIUS servers immediately and the first server which replied back will continue the work with it.
- Active-passive (failover) - upon authentication attempt, the request is sent to the primary server, in case it didn't respond within specified timeout/retries we send the request to the secondary server.