Your default DNS is that of the access provider, but you can change this if there is a problem in the DNS of the provider and use a public DNS. Which is the case with Google Public DNS.
Following the lines to add into “resolv.conf” file.
nameserver 8.8.8.8
nameserver 8.8.4.4
If you don’t know to do it, look here: [CommandLine] – How to change DNS/resolv.conf into ubuntu ? How don’t lost the changes after reboot the system?