By default, people will be able to transfer characters, tamed dinos and items between your clustered servers. If you want to restrict what can be transferred, you have access to these command line options that you can specify when launching your servers.

?PreventDownloadSurvivors=True
Disable downloading characters from the cluster to this server.

?PreventDownloadItems=True
Disable downloading items from the cluster to this server.

?PreventDownloadDinos=True
Disable downloading tamed dinos from the cluster to this server.

?PreventUploadSurvivors=True
Disable uploading characters to the cluster from this server.

?PreventUploadItems=True
Disable uploading items to the cluster from this server.

?PreventUploadDinos=True
Disable uploading tamed dinos to the cluster from this server.