Identify Microsoft data center in use, and GEO DNS

article #778, updated 1844 days ago

Do this:


The resultant real hostname, will identify the actual data center in use. You will notice how this changes according to the Internet DNS servers being treated as authoritative; Microsoft calls this GEO DNS, meaning geographically-appropriate DNS.

Choosing the DNS servers for your ISP — presuming that your ISP has good DNS — will result in much better performance in Microsoft and many other web-based applications. If the ISP does not have good DNS, sometimes DNS servers of the company upstream from your ISP, will serve well.

The opposite of GEO DNS, is the use of DNS servers from the like of Google (, OpenDNS (, and others. Use of best GEO DNS can mean the difference between unusability (>300 ms ping for Office365) and excellence (50 ms).