What is DNS?

If you’re in the web development or systems administration world, you are no stranger to DNS. DNS stands for Domain Name Service and is usually something that clients have no need to understand. By clients, I mean workstations, laptops and everyday users. But sometimes DNS is something that you may need to understand when troubleshooting network connectivity.

Very simply, DNS uses a concept called NAT (Network Address Translation), to translate a domain, such as thatdamnpc.com to an IP address that can be located on the web or a local area network.

In order for DNS to work, there must be a server that "knows" where servers, websites and other devices with a "name" are located. This is where DNS servers come into play. DNS servers are a part of a global network of other DNS servers that share information with each other. When a website is moved from one server to another, the global DNS "cluster" is alerted to the change and the new address and they begin to update themselves with the new information. This process can take about 24 hours before everything is updated worldwide.

Windows has its own DNS cache, or information that it has gotten from it’s own DNS server. If you have a home wireless network, or if you work on a LAN at work, the DNS server is probably an element of your router.

The Windows XP cache, for instance, is supposed to refresh its information every two minutes. This sometimes works, but often times it doesn’t. There is a way, though, to force Windows XP to get all new DNS information. This information may not be different thaan what is already cached in Windows, but if there is a change in website or a new server has come online on your local network and you simply don’t seem to be able to reach it, you can always issue the following command from the Windows commandline:

ipconfig /flushdns

This takes about a second and refreshes the DNS cache for your local machine which could prove helpful:

C:\Documents and Settings\brazeaa>ipconfig /flushdns
Windows IP Configuration
Successfully flushed the DNS Resolver Cache.


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