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STATUS_DS_FLAT_NAME_EXISTS_IN_FOREST
The forest already contains that flat domain name
The flat name is the legacy NetBIOS-style name used by many compatibility paths. Active Directory prevents two trusted domains in a forest from using the same flat name because clients and trusts must resolve it unambiguously.
This can surface during trust creation, domain add, migration, or domain rename planning. Check both current domains and stale trust metadata before choosing a replacement name.
What to inspect
- Search for existing trustedDomain objects using the flat name.
- Compare DNS names and NetBIOS names separately; uniqueness requirements are not identical.
- Review domain rename artifacts and decommissioned domains.
References
- Microsoft: Rendom domain rename tool
- Microsoft: Active Directory FSMO roles
- Microsoft Open Specifications: NTSTATUS values
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