Automatic detection of site membership for domain controllers

During the promotion of a server to domain controller, DCPromo (the wizard used for the promotion process) determines the site the domain controller will become a member of. If the domain controller being created is the first in a new forest, a default site named "Default-First-Site-Name" is created and the domain controller becomes a member of this site until appropriate subnets and sites are configured.

An administrator can (and should) create sites in order to effectively use the bandwidth of Local Area Network (LAN) and Wide Area Network (WAN) connections. After the administrator has created sites and associated subnets with those sites, subsequent domain controller promotions are placed into the appropriate sites automatically. During server promotion, DCPromo queries the domain controller that is acting as the source server for site data. If the IP address of the server being promoted falls within the range for a given subnet defined in the Active Directory, DCPromo configures the membership of the domain controller in the site associated with that subnet.

If no subnet objects are defined or the IP address of the server does not fall within the range of the subnet objects present in the Active Directory, the server is placed in the source domain controller's site.

A domain controller's membership is determined automatically only when it is promoted. If the domain controller is moved from one site to another, the administrator must use the Active Directory Sites and Services manager to move the domain controller's server object to the new site.

Domain controllers that are multi-homed belong to only one site; this site is selected at random during the promotion process. The administrator can move the server from the site selected after the domain controller has been restarted by using the Active Directory Sites and Services Administration tool.

If a domain controller is physically placed in one site, but is configured for membership in another site, the Knowledge Consistency Checker (KCC) that is responsible for building the intra-site and inter-site replication topology considers the domain controller in the site that it is configured for in the Active Directory.

To Move a Domain Controller to Another Site

1. On the Programs menu, point to Administrative Tools, and then click Active Directory Sites and Services.
2. Expand the Sites node and the node that correlates to the site in which the domain controller resides. Expand the Servers node to display the list of domain controllers currently configured for that site.
3. Right-click the domain controller to be moved, and then click Move.
4. Select the appropriate target site, and then click OK.
   

After these steps have been completed, the domain controller's server object (and all child objects) are moved to the new site. The domain controller updates the DNS server with new Service Location (SRV) records and the KCC creates and deletes replication connection objects as needed to adjust the intra-site and inter-site replication topology.