I am performing cross forest migration from 2 AD forests, multiple domains into a new AD forest. When I added one of the domains within a source forest I received the following error:
ADMT is unable to connect to domain controller
\\domaincontroller.sourcedomain.local, in domain sourcedomain.local. Access is denied.
Morgan Che posted up multiple causes for this error on the following forum thread:
I had a different problem to the ones mentioned on the above forum thread. One of my forests was setup with whats called a single labelled domain name. ADMT was having difficulties communicating with all domains within the single labelled forest.
To resolve this on the ADMT server I needed to add a DWORD registry key "AllowSingleLabelDnsDomain" with a decimal value of 1.
ADMT was then able to communicate with all domains in the forest which had a single labelled root domain.
For more information on this registry key please see: