What Is a DNS Lookup?

Let us consider what happens when a user types 'http://www.vicomsoft.com' into their browser:

First of all, in order to communicate over the Internet, the computer that the browser is installed on (client computer) must know the address of at least one DNS server in the world. This address is entered manually when TCP/IP is configured. The client computer extracts the full host name from the URL, in this case 'www.vicomsoft.com', and asks the DNS server to return the IP address of this host. This DNS server will then remove the host-specific part of the name and look for the IP address of 'vicomsoft.com'. If it does not know, it will ask another DNS server which may in turn forward the request to yet another DNS server. This process continues until one of the servers knows the address or until the root ".com" server gets the request. There is only one of these in the world for the top level ".com" domain. It knows all of the IP addresses of all of the ".com" domain names that exist. It returns the IP address of the DNS server at 'vicomsoft.com' to the requesting DNS server which returns it to the previous DNS server and so on right back to the originating DNS server.

Are you still with us? By this time, the originating DNS server (the one contacted by the browser) knows the IP address of the DNS server at 'vicomsoft.com'. So it asks the DNS server at 'vicomsoft.com' for the exact address of the host known as 'www.vicomsoft.com'. The originating DNS server can now return this address to the browser. The browser then sends out its page request using this unique numerical address allowing any routing device on the Internet to correctly send the request to the desired destination.

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