[Edit]: You have to access http://www.astaro.com/kb first or else the direct link to the KB-article won't work!
It implies that only the ASG (Astaro network appliance) supports this feature. I have an ASG in our company, incl. the manual, which shows how to activate that feature on an ASG. I'll get the manual tomorrow, when I'm back in office and I'll try that on my test-machine at home.