You want to move the ISTG for a site to another domain controller. This happens automatically if you take the current ISTG offline, but you may want to transfer the role to a server that is more optimal in your environment.
Open ADSI Edit.
Connect to the CNC if it is not already displayed in the left pane.
In the left pane, browse the Configuration NC Sites.
Click on the site you want to transfer the ISTG for.
In the right pane, double-click CN=NTDS Site Settings.
Modify the interSiteTopologyGenerator attribute to include the NTDS Settings object of the domain controller you want to transfer the ISTG role to.
' This code forces a new ISTG in a site. ' ------ SCRIPT CONFIGURATION ------ ' Name of site to transfer ISTG in strSiteName = "<SiteName>" ' e.g. Raleigh ' Site the new ISTG server is in strNewISTGSite = "<ISTGSiteName>" ' e.g. Raleigh ' Common name of server object for new ISTG strNewISTGName = "<DomainControllerName>" ' e.g. dc01 ' ------ END CONFIGURATION --------- set objRootDSE = GetObject("LDAP://RootDSE") set objSiteSettings = GetObject("LDAP://cn=NTDS Site Settings,cn=" & _ strSiteName & ",cn=sites," & _ objRootDSE.Get("ConfigurationNamingContext")) strCurrentISTG = objSiteSettings.Get("interSiteTopologyGenerator") objSiteSettings.Put "interSiteTopologyGenerator", _ "cn=NTDS Settings,cn=" & strNewISTGName & _ ",cn=servers,cn=" & strNewISTGSite & ",cn=sites," & _ objRootDSE.Get("ConfigurationNamingContext") objSiteSettings.SetInfo WScript.Echo "ISTG for " & strSiteName & " changed from:" WScript.Echo " " & strCurrentISTG WScript.Echo "To" WScript.Echo " " & objSiteSettings.Get("interSiteTopologyGenerator")
The current ISTG for a site is stored in the interSiteTopologyGenerator attribute of the site's NTDS Site Settings object. The distinguished name of the ISTG's NTDS Settings object is stored in that attribute.
Domain controllers communicate their presence as the ISTG by writing to the interSiteTopologyGenerator attribute at a set interval. If you want another domain controller to assume the role of the ISTG, you need to write the distinguished name of that domain controller's NTDS Settings object to the interSiteTopologyGenerator attribute of the NTDS Site Settings object for the site.
Two registry settings govern the ISTG registration process, both of which are stored under the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\NTDS\Parameters key. The interval (in minutes) in which the current ISTG should write to the interSiteTopologyGenerator attribute to inform the other DCs in the site that it is still the ISTG is stored in the KCC site generator renewal interval (minutes) value. The default is 30 minutes. The other value is named KCC site generator fail-over (minutes) and contains the time in minutes that each domain controller in the site should wait for the interSiteTopologyGenerator attribute to be written to before attempting to register itself as the ISTG. The default is 60 minutes.
MS KB 224815 (The Role of the Inter-Site Topology Generator in Active Directory Replication)