April 19th, 2010
Problem.
When running a DCDIAG report on Windows 2003 Domain Controller which is in a child domain the following error is seen.
Starting Test : FsmoCheck Warning : DcGetDcName(PDC_REQUIRED) call failed, error 1355 A Primary Domain Controller could not be located. The Server holding the PDC role is down.Resolution
The error is because DCDIAG is trying to connect to the PDC Emulator in the Parent Domain on port 389UDP. Ensure that any firewall between the root domain controllers and the child domain controllers allows traffic on this port