Repadmin indicates Read-Only Domain Controller in Windows Server 2008


We are all aware how helpful the repadmin tool has become (available thru Windows Support Tools in Windows Server 2003 and earlier) for troubleshooting the replication issues. In Windows Server 2008, this tool along with others come pre-packaged within the OS. You no longer have to install the Support Tools to rein in the benefits of handy command line tools such as, dcdiag, netdiag, rendom and many others.

Here is one repadmin syntax I have become used to as it gives me a snapshot of source DCs and the Destination DCs and their replication status. The command is repadmin /replsum

In above scenario there are two DCs (both Windows Server 2008) showing their latest largest delta times. The Source DC is one that changes have gone out from, where as Destination DC is one who adopted changes from other DC, hence replicated.

What needs to be noticed here is under normal circumstances both DCs would show up under Source and Destination, but since the VM08-02 is a read-only domain controller it can only grab changes from other DC and can’t replicate changes out from it. It only shows up under Destination DC and shows that it was at the receiving end of applying changes to it in terms of Active Directory replication. While read-write domain controller (RWDC) shows changes replicated out from it i.e VM08-01.

The fail/total %% and error column comes very handy when somewhere out there one of your DC has stopped talking to others or hasn’t been talked to due to an issues such is incorrect firewall settings.

Repadmin is one handy tool that all AD Admins should invest a little time learning. For more information on repadmin /showrepl command, click here.