Server migration can occur across domains and forests, although you can’t migrate some roles that depend on AD DS. Reasons for migrating domains and forests include organizational changes, mergers, and consolidation of regional locations. The Active Directory Migration Tool (ADMT) facilitates migration of objects across domains and across forests. Migrating objects between forests is known as an interforest migration; migrating objects between domains within the same forest is known as intraforest migration.
A trust relationship is typically created for both interforest and intraforest migration. The trust enables ADMT to migrate computer resources between domains. Interforest trusts are called Forest Trusts and can be a one-way trust or a two-way transitive trust.
Domain Trusts come in various forms and with various transitive properties. These include external trusts for domains between forests, shortcut trusts that exist between domains within a forest, and realm trusts for relationships between Active Directory domains and non-Windows Kerberos version 5 (V5) realms.
ADMT migrates computers between domains and forests after a trust is established. Each computer requires a restart after moving between domains, so this should be accounted for when planning migration.
