Your DNS cache stores the locations (IP addresses) of web servers that contain web pages which you have recently viewed. If the location of the web server changes before the entry in your DNS cache updates, you can no longer access the site.
If you encounter a large number of HTML 404 error codes, you may need to clear your DNS cache. After you clear your DNS cache, your computer will query nameservers for the new DNS information.
To clear your DNS cache if you use CentOS, run the following command:
systemctl restart dnsmasq.service
If the command succeeds, the system does not return any output.