Active Directory Cookbook

3.9. Finding the Closest Domain Controller

Problem

You want to find the closest domain controller for a particular domain.

Solution

Using a command-line interface

The following command finds the closest domain controller in the specified domain (<DomainDNSName>). By default, it will return the closest DC for the computer nltest is being run from, but you can optionally use the /server option to target a remote host. You can also optionally specify the /site option to find a domain controller that belongs to a particular site.

> nltest /dsgetdc:<DomainDNSName> [/site:<SiteName>] [/server:<ClientName>]

Using VBScript

' This code finds the closest domain controller in the domain
' that the computer running the script is in.
' ------ SCRIPT CONFIGURATION ------
strDomain = "<DomainDNSName>"  ' e.g. emea.rallencorp.com
' ------ END CONFIGURATION ---------

set objIadsTools = CreateObject("IADsTools.DCFunctions")
objIadsTools.DsGetDcName( Cstr(strDomain) )
Wscript.Echo "DC: " & objIadsTools.DCName
Wscript.Echo "DC Site: " & objIadsTools.DCSiteName
Wscript.Echo "Client Site: " & objIadsTools.ClientSiteName

Discussion

The DC locator process as described in MS KB 314861 and MS KB 247811 defines how clients find the closest domain controller. The process uses the site topology stored in Active Directory to calculate the site a particular client is in. After the client site has been identified, then it is a matter of finding a domain controller that is either a member of that same site or that is covering ...