Hi all, I have 2 already created domains and I want to make authentication between them to enable users from the first domain to login with their accounts into the second domain. Is that possible with the current status or I have to make one as a child form the another one? or there is any other way even if I have to reinstall one them again

you would need a two way trust between the domains so that users can authenticate in each other domain. see http://technet.microsoft.com/en-us/library/cc961481.aspx for info. you dont have to be child domain for that, so no need for reinstalling anything

Hi, Thanks for replying. is that solution valid if one of them Server 2003 and the other 2008

Hello, Yes. You can created a trust between a 2003 and a 2008 domainsIsaac Oben MCITP:EA, MCSE

Hi, If these two domains are in the same forest, it is not necessary to create a trust. Only the domains in different forests need to create a trust. Parent–Child and Tree–Root two-way trusts are created automatically during the Domain Control promotion and you can access the resource cross the domain directly. If there are two domains in two forests, you need to configure the DNS Server for communication between domains, you have three options to provide cross-forest name resolution below: l conditional forwarders l secondary zones l stub zones By the way, if this is a Tree–Root two-way trust, you also need to configure the DNS Server for name resolution. After that, you need to create a forest trust manually. For more information, please read: Checklist: Creating a forest trust from the following link: http://technet.microsoft.com/en-us/library/cc756852%28WS.10%29.aspx For more information about accessing resources across domains, please refer to the following link: http://technet.microsoft.com/en-us/library/cc787646(WS.10).aspx Regards, Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.