The resolver is a set of routines in the C library that provide access to the Internet Domain Name System (DNS). The resolver configuration file contains information that is read by the resolver routines the first time they are invoked by a process.
To see your DNS server address type following command as shell prompt:
$ cat /etc/resolv.conf
OR
$ less /etc/resolv.conf
nameserver 208.67.222.222
nameserver 208.67.220.220
Where, nameserver 208.67.222.222 : It is Name server IP address (in dot notation) of a name server that the resolver should query. All your application will use this IP address for DNS purpose.