Repadmin monitors the replication in your Active Directory Forest, you can read this AskDs post about this tool. The command line “repadmin /replsum” helps you retrieve the global forest replication status. The data retrieved for a given Domain Controller is:

• Largest Delta: longest time since he successfully replicated all the Naming Contexts with his replication partners.
• Number of failed replications that occured for all the Naming Contexts (aka Directory Partitions) with his replication partners.

The purpose of the powershell script is to analyse DC’s inbound replication thanks to the command line “repadmin /replsum /bydest”. If there are RODCs in your domain they do not show up if you use the /bysrc switch. You can read this post if you need to know more about running the repadmin /replsum command in a domain with RODCs.

If for a given DC the “largest delta” exceeds a given threshold (in minutes), or there are replication failures, we will read on the RootDSE object the msDS-ReplAllInboundNeighbors attribute. With that information we will retrieve which replication partners and “Naming Contexts” that are having trouble to replicate. You can retrieve the same type of information with the “replsum /showrepl %dc_name% /csv” command line, but the data stored in the msDS-ReplAllInboundNeighbors attribute is in XML format, which easy and convenient to manipulate with Powershell.

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