When you promote a domain controller, Windows 2000 evaluates the subnet that the server is in to determine which site the server is a member of. The default behavior is to permit membership in a single site.
If you wish a domain controller to advertise its' services in multiple sites, to provide some fault tolerance, or to configure a domain controller for membership in multiple sites:
1. Use Regedt32 to navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters.
2. On the Edit menu, Add Value name SiteCoverage, as a REG_MULTI_SZ data type. For each additional site, type the site name into a separate line:
Second site name
Third site name
Fourth site name