Network Troubleshooting for Beginners: The Internet’s Phone Book (DNS)

Introduction

You’ve gone through all the checks from the previous articles:

• The computer has the correct IP address (ipconfig).
• The router responds (ping 192.168.1.1).
• Ping to a public address (ping 8.8.8.8) works.

Looks like the internet is fine! But the browser won’t open google.com. 🤔 Welcome to the most common cause of such issues — DNS failures.

What is DNS? 📖

The internet runs on IP addresses (e.g., 142.250.184.110), but people prefer names (google.com).

DNS (Domain Name System) is the global “phone book” that translates domain names into IP addresses. If DNS doesn’t work — you won’t reach a website, even if the connection is fine.

Today we’ll master two tools to check DNS: nslookup and dig.

nslookup — Simple Directory

What does it do?

Asks a DNS server a question and shows the response.

Usage

nslookup google.com

Successful response

Server:  _gateway
Address: 192.168.1.1

Non-authoritative answer:
Name:    google.com
Addresses: 2a00:1450:4001:82e::200e
          142.250.184.110

• Server/Address — the DNS server that responded (usually your router).
• Name/Addresses — the requested name and the resolved IPs.

Error

*** _gateway can't find google.com: Non-existent domain

The DNS server couldn’t find the address.

Trick: ask another DNS

nslookup google.com 8.8.8.8

If it works with 8.8.8.8 but not with your default — the issue lies with your ISP/router’s DNS.

👉 Conclusion: nslookup is a quick way to check if your PC can translate names into IPs.

dig — Advanced Directory

What does it do?

Provides a detailed report of a DNS query. Popular with admins. It’s usually available on Linux/macOS, and can be installed on Windows.

Usage

dig google.com

Key parts of the output

;; QUESTION SECTION:
;google.com.                    IN      A

;; ANSWER SECTION:
google.com.             242     IN      A       142.250.184.110

;; SERVER: 192.168.1.1#53(192.168.1.1)

• QUESTION SECTION — what was asked.
• ANSWER SECTION — the resolved IP address.
• SERVER — who answered.

Query another DNS

dig @8.8.8.8 google.com

👉 Conclusion: dig gives more detail and is useful for tricky cases.

Conclusion

Congrats! You now know how to check if the internet’s “phone book” is working.

• nslookup — fast and simple tool.
• dig — powerful and detailed for deeper diagnostics.

If DNS works, the site’s IP is known, and ping succeeds — but the browser still won’t open the page? The server may be reachable, but the required service (e.g., web server) isn’t responding.

What’s Next?

In the next article, we’ll explore how to check if the “right door” is open on the server. For that, we’ll get to know telnet and nc (netcat).

Resources

• nslookup (Windows)
• dig man page
• Google Public DNS (8.8.8.8)