Normally replication fails, if it doesn’t have enough bandwidth to complete the scheduled replication, you can use the below command to Sync the Active Directory replication between two domain controllers in low bandwidth sites.
repadmin /replicate destination_dsa source_dsa Naming Context /async
repadmin /replicate server2.test.com server1.test.com dc=test,dc=com /async
Destination server Name: server2.test.com
Source server Name: server1.test.com
Naming Context : dc=test,dc=com (Domain partition)
/async switch to specifies that the replication will be asynchronous.
This means that Repadmin starts the replication, but it does not expect an immediate response from the destination domain controller. Use this parameter when there are slow links between domain controllers.
Run this command and check for replication event in Directory services event log, if you get the RPC error then you have to run the command again, you need to follow this procedure till the replication gets completes
Note: This will help only for some scenarios; if you have very low bandwidth sites then this will not help, you have to resolve the network issue or have to upgrade the network bandwidth in order to complete the Active Directory replication.
Force active directory replication
use the same command to Force active directory replication without /async for Sync Active Directory replication between two domain controllers in normal bandwidth