Old EC server is on Server 2016 with Server 2025 due imminent. Different hardware approaching end-of-life. The OS in-place upgrade path Microsoft doesn’t support for the EC role. Whatever the…
How to read the current Active Directory forest functional level (FFL) and domain functional level (DFL), what each level unlocks, the pre-flight checklist before raising, and how to actually raise it with Set-ADForestMode / Set-ADDomainMode. Includes the schema-version-to-OS table, a decision flow for whether to raise, and the common pitfalls (forgotten DCs, Server 2019/2022 reporting Windows2016Forest, irreversibility).
