DNS : Its working

 

In Network, the hosts primarily communicate between each other through IP addresses.

 

 For example, google search from your local PC, your computer is actually communicating with the IP address of one of the web servers of google.com. However, even if the computer is efficient with numbers, humans on the other hand work better with names. For this reason, the TCP/IP protocol includes the Domain Name System (DNS)  to link between IPs and computer names i.e. hostnames.

 

 The DNS is a distributed database of computers that is responsible for resolving hostnames against IP addresses and vice-versa.

Any DNS query involves two parts.

1. The Resolver: The resolver forms up or initiates the query. The resolver itself does not run as a program. /etc/resolv.conf is an example of a resolver.
2. Name Server: The Name Server is the service running in the server that responds to the DNS query generated by the resolver i.e. answers to the question of the resolver.
    =========
   1. nslookup
       >> nslookup followed by the domain name will display the “A Record” ( IP Address ) of the domain.
   
   Eg: nslookup redhat.com
   2. Query the MX Record using -query=mx
   nslookup -query=mx redhat.com
   
   nslookup -type=ns redhat.com
   nslookup -type=soa redhat.com
   nslookup -type=any google.com
   nslookup 209.132.183.181
   nslookup redhat.com ns1.redhat.com
   nslookup -port 56 redhat.com
   nslookup -timeout=10 redhat.com
   
   
   dig Hostname
   dig DomaiNameHere
   dig @DNS-server-name Hostname
   dig @DNS-server-name IPAddress
   dig @DNS-server-name Hostname|IPAddress type
   
   For more info
   Please visit
   
   http://www.cyberciti.biz/faq/linux-unix-dig-command-examples-usage-syntax/