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A buddy asked me this question - and I quite honestly don't know enough about Active Directory and how to operate/configure AD to answer this.

A customer of my buddy has an AD domain DomainA and that's what's they use to sign on to Active Directory now - users sign in with their user name in the form of DomainA\John Doe.

For whatever reasons (don't ask me for those reasons!), they know what to logon with a different domain name (which is not a subdomain of the first domain) - let's say OtherDomain. So the idea is: the Active Directory still runs on DomainA, but the users log in using OtherDomain\John Doe.

Any chance this is even possible? If so: how do you set this up / configure such a scenario?

Thanks for any hints!

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up vote 4 down vote accepted

This is possible. It's called a UPN and can be whatever you want.

In Active Directory Domains and Trusts you can define a new UPN for your forest. It then becomes select-able on the Account tab of a user account in ADUC. So if your domain is Domain1 and you define domain2.whatever as a UPN suffix for a user, that user can log in as user@domain2.whatever

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OK - but can they log on as domain2\user (NetBIOS-style), too? Or only using the UPN name user@domain2.whatever ?? – marc_s Oct 17 '12 at 14:41
That, I'm not 100% user about. You can change the NetBIOS name for a whole domain, but I don't believe that changing the UPN for a user will allow that specific format to work. – MDMarra Oct 17 '12 at 14:42
UPN only affects the "@" style name. You can't change the NetBIOS style login. – Chris S Oct 17 '12 at 14:56
@ChrisS: OK thanks - what if I had a second domain OtherDomain and established full, two-way trust between both domains. Could users log on to DomainA using OtherDomain accounts? – marc_s Oct 17 '12 at 20:28
If you had two domains DomainA and DomainB, with trusts, users from the trusted domain can log-in to the trusting domain. But users still can't use the "wrong" domain in their login credentials. So if users exist in DomainA, they can not login using "DomainB\User" as they still don't exist in DomainB. – Chris S Oct 18 '12 at 19:16

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