We recently acquired a company running a very similar domain to ours, and we would like to merge the company into our domain.
The question is, can we provide a domain alias and map that to our domain (e.g. ComapnyA\username -> CompanyB\username) meaning we don't have to implement the new domain on the old machines.
Or do we have to maintain 2 domain forests?
The acquired company uses a username format of JoeB wheras we use JBloggs can we map the users to a specific user on the domain?
In the short term, clearly a trust is the way to go. In the long term, you are almost certainly going to have to migrate their AD to yours. You will probably do it using the Active Directory Migration Tool and the Password Export Server.
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=20c0db45-db16-4d10-99f2-539b7277ccdb http://www.microsoft.com/downloads/en/details.aspx?familyid=F0D03C3C-4757-40FD-8306-68079BA9C773&displaylang=en
I suggest that you read this document Microsoft on how to use the ADMT and restructuring domains.
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=6D710919-1BA5-41CA-B2F3-C11BCB4857AF
This isn't a strong suit for me, but you might try looking into AD Sites and Services. There is a way that you can trust a domain and it would essentially be an extension of your domain. I dont know if it would be able to login with JoeB on JBloggs network. Just a thought.
Probably you want to cresate a Trust between domains. MS KB on this. Probaly you'll need to investigate this more as it's is supposed to be quite painfull to do this properly.