Troubleshooting DNS issues

DNS issues are typically rare, except in the case of an invalid configuration. In most cases, any troubleshooting you do would be done on your local DNS servers, as public DNS servers on the Internet are outside of your control. In the case of an external DNS server failing, such as that from your ISP, your only recourse might be to use a different DNS provider, such as utilizing Google's public DNS addresses of 8.8.8.8 and 8.8.4.4. But in the case of your local DNS server failing, you have more control.

As always, you would start troubleshooting DNS issues by checking whether or not you can reach the DNS server. First, check /etc/resolv.conf to see which DNS server your machine is using. Is it the correct server? If not, correct this in your network scripts and restart networking. If it is the correct server, can you reach it? Try a simple ping, and as long as the server is configured to respond to ICMP echo requests, you should see a response. If you can reach...