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Understanding and Using DNS Tools for Troubleshooting

Written by Trisul ·

DNS (Domain Name System) is the backbone of the internet, translating human-friendly domain names into IP addresses. When something goes wrong with a website or network, DNS issues are often the culprit. In this guide, you'll learn how to use essential DNS tools—both command-line and online—to diagnose and fix common problems.

Why DNS Troubleshooting Matters

  • Quickly identify if a site is down for everyone or just you
  • Check if DNS records (A, CNAME, MX, TXT) are correct
  • Spot propagation delays or misconfigurations
  • Ensure emails and web services work reliably

Essential DNS Tools

  • nslookup: Built into Windows, Linux, and macOS. Simple and fast for quick lookups.
  • dig: More advanced, gives detailed DNS record info.
  • host: Another command-line tool, great for quick checks.
  • Online tools: Websites like MXToolbox, DNSChecker, and Google Admin Toolbox.

How to Use nslookup

nslookup trisulk11.in
nslookup -type=MX trisulk11.in
nslookup -type=TXT trisulk11.in

Tip: Use server x.x.x.x in nslookup to query a specific DNS server.

How to Use dig

dig trisulk11.in
dig MX trisulk11.in
dig @8.8.8.8 trisulk11.in ANY

Tip: +short gives concise answers: dig trisulk11.in +short

Checking DNS Propagation

When you update DNS records, changes can take time to propagate. Use online tools to check from multiple locations:

Common DNS Issues & Solutions

  • Site not loading? Check if the A record points to the correct IP.
  • Email not working? Verify MX and SPF/TXT records.
  • SSL errors? Make sure CNAME and A records are correct for your certificate provider.
  • Propagation delays? Wait for TTL to expire, or check with multiple DNS servers.

Bonus: Flush Local DNS Cache

// Windows
ipconfig /flushdns

// macOS
sudo killall -HUP mDNSResponder

// Linux (varies)
sudo systemd-resolve --flush-caches

Conclusion

Mastering DNS tools like nslookup and dig empowers you to troubleshoot network and website issues quickly. Combine command-line checks with online tools for a complete picture, and you'll resolve DNS problems with confidence.

Have a DNS troubleshooting tip or question? Leave a comment or contact me!