DNS request are usually cache, that’s good as it speeds up the lookups within the same host but sometimes we will want to clear the cache so it don’t hold the values that are no longer valid.
In Leopard (Mac OSX 10.5) or Snow Leopard (10.6)
To clear DNS cache in Leopard, just type this in your Terminal and hit enter.
To Clear DNS cache in Mac OS X Tiger
Use the following command:
What is DNS?
The Domain Name System (DNS) is a naming system for computers, and anything else on the Internet. When you type a website’s name into your browser address bar, the DNS gives you the IP co-ordinates to find the server.