I recently started administering an OS X server (10.8) that is on the same network as our AD domain. While setting up Mac Share Points, I encountered some odd behavior that I hope someone can explain. For the purposes of this example assume the following:
1) Local User on OS X Server: frank, password: Help.2012
2) AD Domain User: frank, password: Help.2012
3) AD Domain: mycompany
4) OS X Server hostname: macserver (not bound to AD, not running OD)
When joined to the domain on a a Win 7 computer and logged in as frank and accessing the shares at \\macserver, it automatically authenticates using frank's OS X credentials (because they are the same). However, if I change frank's OS X password, the standard Windows authentication dialog pops-up preset to use frank's AD domain (my company\frank). However, after entering the new OS X password, it will not authenticate without changing the domain to local (.\frank).
Basically, if a user in AD has the same User name and password in OS X, it will authenticate automatically regardless of the domain. If the passwords differ, authenticating to the OS X shares must be done from the local machine.
(and slightly off topic - how come an OS X administrator can access the root drives on the Mac server from Windows when accessing the Mac shares even when they aren't shared? In other words, it will show all the shared folders from "File Sharing" plus whatever drives are mounted in OS X)