Hi I'm Philipp from Germany,
I'm an active member of a german Microsoft Support Community www.mcseboard.de and a view weeks ago we had an discussion about the global catalog requirement and imho we couldn't found the right answer. Perhaps someone can help me here.
After I had looked at this resources:
TechNet Support WebCast: Overview of universal group caching in Microsoft Windows Server 2003
Global Catalog Server Requirement for User and Computer Logon
Windows Server Hacks: Configuring Universal Group Caching
I got this conclusion, please correct me if I wrote nonsens:
1. W2k Mixed Mode:
No GC is needed for userlogon
2. W2k Native Mode:
GC is needed for userlogon regardless the user belongs to a universal group or a group who is nested in a universal one. This behavior could be changed but that's not recommended. When no GC is online, cached credentials will be used to log on, when credential-caching is disabled logon fails.
3. W2k Native Mode with one or more W2k3 DC`s in the ad:
On the 2k3 DC universal group caching could be enabled but that's not recommended, else as number two.
4. W2k3 Native Mode:
Universal group caching could be activated. When it is... no global catalog is needed for Users who are in the cache. (By default universal group caching is not activated so logon will fail when no GC is there and cached-credentials are deactivated)
BTW: I'm wondering why I don`t find any good resources or KB-Article who gets more in detail or list the global catalog requirement for 2k and 2k3.