The server access mode is fixed to Round-Robin (Direct cannot be configured for operator management). A health-check function is available for operator management, which can optionally be disabled. The health-check polls the server once every 10 seconds with an improbable user name. If the server does not respond to this health-check, it will be marked down.
If the first server in the list cannot find a user, the next server in the RADIUS server list is not queried and access is denied. If multiple RADIUS servers are used, it is assumed they all have the same user database.