According to their blog post, Google Public DNS uses continuous record prefetching to avoid cache misses — hopefully making the service faster — and implements a variety of techniques to block spoofing attempts. They also say that (unlike an increasing number of ISPs), Google Public DNS behaves exactly according to the DNS standard, and will not redirect you to advertising in the event of a failed lookup.
Google DNS Server IP Addresses
The Google Public DNS IP addresses are as follows:
Add Google DNS Server IP Address Under Linux
Edit the /etc/resolv.conf file and add above two ip address: