I figure I’ll keep populating the blog with some brain candy. This is for Windows users, who can often find themselves in trouble when dealing with their mysterious DNS client.
If you’ve been testing out a new domain or subdomain and have somehow queried it (by ping, using a browser, or some other method) before it comes active on the master nameserver, your system’s DNS client will cache the “nope, no host by that name” response it gets until its default expiration time passes, which is usually five minutes. Even if you use nslookup to check the result, and it comes back favorably, the Windows DNS client will cache the NXDOMAIN answer and none of your applications will be able to access it. Assuming the host should be working at the current time, flushing your system’s DNS is a good step you can take towards checking for problems or saving that five minutes so you can continue work right away. To do so on Windows XP:
- close *all* web browser and e-mail clients.
- hit Start, Run…, and enter into the text field ipconfig /flushdns
- try your lookup again.
If after this attempt you’re still having problems, you’ve eliminated your workstation’s cache from the problem and can use nslookup or other tools to check your resolving DNS directly.
Another way around this, though usually not recommended, is to shut off the caching system entirely:
http://support.microsoft.com/kb/318803
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