Issues with the DNS do not always cause an actual error message to surface; rather they may take the form of other symptoms; such as:
- Inability to log on or very slow logon.
- Unable to join a domain or run a logon script.
- Inability to access an IP address.
DNS lookup failed errors may or may not be something that you can correct. These errors can be due to issues with the Internet Service Provider (ISP) or your cache may just be overloaded with negative or conflicting information. Cleaning out your cache is the first thing you can do, which will also let you know whether the error is due to your system or the ISP.
Flushing your cache will empty all the information stored on your computer and start you back at a clean slate. By cleaning out all of the information in the cache, there will be no conflicting information to cause DNS lookup failed errors. To do this, you will need to open the command screen.
For all Windows users except Vista and Windows 7, go to Start > Run. Click Run and in the pop-up box that opens, type: com or command and press Enter.
For Windows Vista and Windows 7 users, go to Start > All Programs > Accessories > Command Prompt. Right-click on Command Prompt and select Run as Administrator.
The remaining instructions are the same for all Windows users. Type ipconfig/flushdns and hit Enter. Once the DNS cache has been flushed, a confirmation window should open stating that the DNS resolver cache was successfully flushed. This should eliminate future DNS lookup failed errors. It is not a bad idea to do this when you begin to experience any of the symptoms listed above.
If you are still experiencing DNS failed lookup errors after you have flushed your cache, then it is likely an error at the ISP end of things. Unfortunately, there is not a lot you can do about this, which means you may not be able to access the site until the error is resolved.