You want to determine if replication is succeeding.
The following two commands will help identify problems with replication on a source domain controller:
> dcdiag /test:replications > repadmin /showrepl /errorsonly
For a more detailed report, you can use the Replication Monitor
replmon.exe). The Generate Status Report option
will produce a lengthy report of site topology, replication
information, and provide details on any errors encountered. The
Directory Service event log can also be an invaluable source of
replication and KCC problems.
Recipe 12.2 for viewing the replication status of several domain controllers