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Exchange relies on DNS quite heavily. Many problems that are blamed on a broken Exchange configuration may in fact be caused by a misconfigured DNS server. If you're upgrading from an older Exchange installation to a newer one -- and migrating to a different DNS server along with it -- one possible way to determine if DNS problems are causing Exchange issues is to export a known-good DNS configuration to the target server.
Unfortunately, Windows has no built-in way to do this. This is doubly annoying if you have special DNS entries for your organization (for instance, if you have single-word DNS entries, also known as "single-label names") or other custom configurations that aren't easy to reproduce manually. Luckily, DNS guru Dean Wells has written a script called DNS Dump that helps get around this problem.
DNS Dump is a command-line batch file that imports and exports DNS information to a structured file, so you can move the DNS entries from site to site. The information exported includes DNS service configuration, Active Directory-integrated zones and zone configuration data (which is important for Exchange), and conventional zone info. Existing AD zones will not be overwritten; however; you may need to manually erase existing AD zone information before running the tool. Non-AD zone information, however, will be erased and overwritten.
Note that DNS Dump can only import a file produced by the same version of DNS Dump. Also be sure to rename the file before you use it so it runs as a batch file -- the current file extension is .cm_ to keep it from being executed accidentally at download.
A side note: Windows Server doesn't require you to use the Microsoft DNS service. It certainly isn't the only choice out there; for instance, there are freeware implementations of the BIND service for Windows. But if you're troubleshooting Exchange issues because of DNS configuration problems and want to reduce the number of variables, it may be best to stick with Microsoft's DNS -- if only as a "better the devil you know" situation.
About the author: Serdar Yegulalp is editor of the Windows 2000 Power Users Newsletter and a regular contributor to SearchExchange.com.
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This was first published in April 2005