Direct replication could not occur between the following source and destination domain controllers because an unsupported ...

Direct replication could not occur between the following source and destination domain controllers because an unsupported intersite transport is configured for the following Connection object. The Connection object representing intersite replication from the source domain controller to the destination domain controller indicates that the writeable directory partition should be replicated over the intersite transport.  
  
Connection object:
%1  
Directory partition:
%4  
Source domain controller:
%2  
Destination domain controller:
%3  
Intersite transport:
%5  
  
Domain controllers in the same domain, but in different sites are required to use the IP transport for replication. Only domain controllers in different domains can replicate using other transports.