OS Auth Forest environment

[cyberbert]

Hello,
when enabling OS Auth I can download and select groups from the server's AD domain.
In our company we have a multidomain forest and the server is in domain A, as well as a user group (GROUP) that I would like to use for authorization. So I select GROUP and grant autorizations. But the user I use for this case (as well as most other users) is located in another domain (B) but still is member of GROUP. When login screen appears, the domain field is greyed out and contains the domain of the computer. But I need to login with a user from another domain, so - in an naive approach - I tried to pass the domain information using <Domain>\<Username> format as well as UPN. Login is denied.
Is there a way OS Auth is working in this setup (multiple domains) or do I have to stick to local usermanagement?

Thanks for any information!

[mkerk]

Hello,
multidomain forest is not supported in WinCC OA.
BR,
Mousser