Your nameserver has changed from ip address
In /etc/resolv.conf which is contained in the resolvconf package, you can find the DNS information.
The resolvconf package makes this /etc/resolv.conf into a symbolic link and manages its contents by the hook scripts automatically.
About the Author
Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux in different European countries and different European languages. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform where he is one of the most important contributors and the main developer.