Tip - DynamicSiteName and SiteName – Which site a client computer belongs to?
If you are troubleshooting a client computer which always communicates to a domain controller in different site, you should look at the two registry entries explained in this article. This article applies to Windows 2000 and Windows XP.
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http://www.windowsnetworking.com/kbase/WindowsTips/Windows2003/AdminTips/ActiveDirectory/DynamicSiteNameandSiteNameWhichsiteaclientcomputerbelongsto.html