The Directory Server’s replication mechanism relies on the server’s location information to reduce protocol traffic on WAN links. During protocol negotiation, the replication server with the highest WAN Gateway priority (priority 1 indicates the highest priority) automatically assumes the role as the WAN Gateway Server for that particular location. The Gateway Server’s main function is to route update messages from other non-gateway servers at the same location to remote WAN Gateway servers at other locations. Similarly, at the destination point, the replication server with the WAN Gateway role will receive update messages from other WAN gateway servers at other locations and push them out to all replication servers at the current location. This setup ensures that all WAN communication flows through the WAN Gateway Servers.
The figure below shows a basic connection configuration for updates. Keep in mind that all of the replication servers are fully connected to each other for monitoring or server negotiation purposes.