What is DNS?

The term DNS stands for Domain Name System. DNS allows a server to be addressed by a domain name. – For example kkomp.com is the domain name of this blog. The DNS nameservers connect the IP address of a server with a domain name in order to make this possible.

When you type http://kkomp.com into your browser bar; the connection request is sent to a DNS server, which translates it into a request for connection to the appropriate IP address. The computer/server at that IP address is then sent the request that you made and responds by sending the data that you asked for.

Using DNS means that you don’t have to refer to every server by its IP address directly: If you had to address this blog as 213.171.218.220 (Old ip address) then you’d have to write it down somewhere along with a note that it’s the IP address of kkomp.com. The DNS server does this for you; so that all you have to remember is kkomp.com.

*This article has no pictures. It’s difficult to know how one might go about getting pictures of DNS.*

What is a DNS cache?

When you visit a website, your computer may store a snapshot of what it finds there in the DNS cache of the DNS Resolver in your local operating system. This allows your computer to display a picture of what it last saw from that location at that IP address; therefore speeding up the time it takes to display it in your browser. Although the image in the local computer’s cache is only a temporary file, you might be viewing a cached image of the website in question rather than the actual content; which could have changed since then.

Flushing the Local DNS Cache

If you flush your local DNS cache; your computer is forced to make another DNS lookup when you request to see a website, as in flushing the DNS cache the locally stored image is deleted, and the computer has to store another one. This is useful if the website content has changed but your computer is still displaying the cached image of how the site looked previously.

Here’s how to flush your local DNS cache: -

(¬ = return.)

In Windows XP:

Click Start>Run.

Type “cmd” and click OK.

Type “ipconfig /flushdns” at the command prompt. (Note the space between “ipconfig” and “/flushdns”.) ¬

The message of confirmation will appear.

Type “exit”. ¬

In Windows Vista:

Right-click the Command Prompt icon and select “Run as Administrator”.

Type “cmd” and click OK.

Type “ipconfig /flushdns” at the command prompt. (Note the space between “ipconfig” and “/flushdns”.) ¬

The message of confirmation will appear.

Type “exit”. ¬

In Mac OSX 10.5.1 or below:

Open a terminal session.

Type “lookupd –flushcache”. ¬

After confirmation that the cache has been cleared; close the terminal session.

In Mac OSX above 10.5.1:

Open a terminal session.

Type “dnscacheutil –flushcache”. ¬

After confirmation that the cache has been cleared; close the terminal session.

Target neutralised.