DCDIAG.EXE /E or /A or /C expected: DC could not be queried error 0x6ba

When two DC replication failed, dcdiag will find the error.

Show like this:

   The event log File Replication Service on server
         dcdiag-2008.margiestravel.com could not be queried, error 0x6ba
         "The RPC server is unavailable."

Reason: 

RPC server doesn't work well.
1 the service don't running
2 the firewall block the service

Solution:

1 start the service
2 enable the firewall in Boundin for these three item:

• Remote Event Log Management (NP-In)
• Remote Event Log Management (RPC)
• Remote Event Log Management (RPC-EPMAP)