Active Directory migration and domain consolidation
Migrated a multi-domain AD forest to a single clean domain, decommissioning legacy DCs and fixing years of accumulated cruft.
Active DirectoryWindows ServerMigrationPowerShell
The situation
A mid-sized organization had grown through acquisitions and ended up with multiple AD domains, stale user objects going back years, GPO conflicts nobody understood, and four domain controllers — two of which were running end-of-life OS versions. Nobody had touched the replication topology since the last sysadmin left.
What I delivered
- Full AD audit: stale users, stale computers, orphaned groups, GPO conflict analysis
- FSMO role inventory and safe migration plan to the surviving DC
- Staged DC decommission with DNS validation at each step
- GPO cleanup: removed 40+ redundant or conflicting policies, documented the ones kept
- New OU structure matching the actual org chart
- Handoff runbook covering daily operations and the “what to do if” scenarios
Outcome
- Single healthy domain controller running a supported OS
- AD object count reduced by 60% (stale cleanup)
- Replication clean with no errors
- IT team can now read their own Group Policy without a forensics session
Environment details generalized. User count and domain names withheld.