Troubleshoot DNS Server Errors

DNS (Domain Name System) server errors, especially the common "DNS server not responding" message, can prevent you from accessing websites and online services. This comprehensive guide will help you identify, diagnose, and fix DNS server issues with step-by-step instructions.

What is DNS? The Domain Name System (DNS) translates human-readable domain names (like example.com) into IP addresses (like 93.184.216.34) that computers use to identify each other on the network. When DNS isn't working properly, you may not be able to access websites even when your internet connection is working.

Diagnosing DNS Server Issues

Before attempting to fix DNS issues, it's important to confirm that DNS is indeed the problem. Follow these steps to diagnose DNS-related problems:

Step 1: Verify Your Internet Connection

First, make sure your internet connection is working properly:

  • Check if other devices on your network can access the internet
  • Try accessing a website by IP address instead of domain name (e.g., try http://93.184.216.34 which is example.com)
  • If you can access websites by IP but not by domain name, it's likely a DNS issue

How to ping a website by IP address:

ping 93.184.216.34

Step 2: Check Your Current DNS Settings

Verify which DNS servers your device is currently using:

  1. Open Command Prompt (search for "cmd" in the Start menu)
  2. Type ipconfig /all and press Enter
  3. Look for "DNS Servers" under your active network adapter
ipconfig /all

Example output:

Ethernet adapter Ethernet: Connection-specific DNS Suffix . : example.com IPv4 Address. . . . . . . . . . . : 192.168.1.100 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.1.1 DNS Servers . . . . . . . . . . . : 8.8.8.8 8.8.4.4

Step 3: Test DNS Resolution

Use these tools to test if DNS resolution is working properly:

nslookup is available on Windows, macOS, and Linux:

nslookup example.com

Example successful output:

Server: dns.google Address: 8.8.8.8 Non-authoritative answer: Name: example.com Address: 93.184.216.34

Example failed output:

Server: dns.google Address: 8.8.8.8 *** dns.google can't find example.com: Non-existent domain

How to interpret the results:

  • Successful resolution: The tool returns an IP address for the domain name
  • Failed resolution: You'll see errors like "Non-existent domain," "SERVFAIL," or "REFUSED"
  • Timeout: The DNS server didn't respond within the expected time

Common DNS Server Errors and Solutions

DNS Server Not Responding

This common error occurs when your device cannot communicate with the DNS servers, resulting in the "DNS server not responding" message.

Symptoms: "DNS Server Not Responding" error message in your browser or network settings, websites won't load but your internet connection appears to be working

How to Fix:

  1. Restart your router and modem
    • Unplug both devices from power
    • Wait 30 seconds
    • Plug in the modem and wait for it to fully connect
    • Plug in the router and wait for it to boot up
  2. Check your internet connection
    • Try connecting to other websites
    • Check if other devices on your network can access the internet
  3. Use alternative DNS servers (instructions in the "Changing DNS Servers" section below)
  4. Flush your DNS cache (instructions in the "How to Flush DNS Cache" section below)

DNS_PROBE_FINISHED_NXDOMAIN

This error indicates that the domain name you're trying to access doesn't exist or cannot be resolved by DNS servers.

Symptoms: "DNS_PROBE_FINISHED_NXDOMAIN" error in Chrome, "Server not found" in Firefox, or similar errors in other browsers

How to Fix:

  1. Check if the website address is correct
    • Verify the spelling of the domain name
    • Try accessing the website from a search engine result
  2. Clear your browser cache and cookies
    • Chrome: Settings > Privacy and security > Clear browsing data
    • Firefox: Options > Privacy & Security > Cookies and Site Data > Clear Data
    • Edge: Settings > Privacy, search, and services > Clear browsing data
  3. Flush your DNS cache (instructions in the "How to Flush DNS Cache" section below)
  4. Temporarily disable your firewall or antivirus

    Note: Only do this temporarily for testing purposes, and remember to re-enable it afterward

DNS_PROBE_FINISHED_BAD_CONFIG

This error suggests there's a problem with your DNS configuration.

Symptoms: "DNS_PROBE_FINISHED_BAD_CONFIG" error message, unable to access any websites

How to Fix:

  1. Reset your network adapter
    1. Open Command Prompt as Administrator
    2. Type the following commands and press Enter after each:
      netsh winsock reset netsh int ip reset ipconfig /release ipconfig /renew
    3. Restart your computer
  2. Change your DNS servers (instructions in the "Changing DNS Servers" section below)
  3. Update your network drivers
    • Windows: Device Manager > Network adapters > right-click your adapter > Update driver
    • macOS: System updates will include network driver updates
    • Linux: Use your distribution's package manager to update
  4. Reset your TCP/IP settings (see the network adapter reset instructions above)

How to Flush DNS Cache

Your computer stores previously resolved domain names in a local DNS cache to speed up future requests. Sometimes this cache can become corrupted or contain outdated information. Flushing the DNS cache can resolve many DNS-related issues.

Windows:

  1. Open Command Prompt as Administrator
  2. Type the following command and press Enter:
    ipconfig /flushdns
  3. You should see a confirmation message: "Successfully flushed the DNS Resolver Cache"

Changing DNS Servers

Sometimes, your ISP's DNS servers may be slow or experiencing issues. Using alternative DNS servers can improve your browsing experience and resolve DNS-related problems.

Google DNS

Primary: 8.8.8.8

Secondary: 8.8.4.4

Fast and reliable, maintained by Google

Cloudflare DNS

Primary: 1.1.1.1

Secondary: 1.0.0.1

Focus on speed and privacy, maintained by Cloudflare

How to Change DNS Servers

  1. Open Control Panel > Network and Internet > Network and Sharing Center
  2. Click on your active connection (e.g., "Wi-Fi" or "Ethernet")
  3. Click "Properties"
  4. Select "Internet Protocol Version 4 (TCP/IPv4)" and click "Properties"
  5. Select "Use the following DNS server addresses"
  6. Enter your preferred DNS servers (e.g., 8.8.8.8 for Preferred, 8.8.4.4 for Alternate)
  7. Click "OK" to save changes

Advanced Troubleshooting Techniques

Check for Firewall or Antivirus Interference

Sometimes firewalls or antivirus software can block DNS queries:

  1. Temporarily disable your firewall or antivirus software
  2. Try accessing websites to see if the DNS issues are resolved
  3. If this fixes the problem, add exceptions for DNS traffic (UDP/TCP port 53) in your security software
  4. Remember to re-enable your security software after testing

Check for DNS Hijacking or Malware

Malware can sometimes redirect your DNS queries to malicious servers:

  1. Run a full system scan with your antivirus software
  2. Use specialized anti-malware tools like Malwarebytes
  3. Check your hosts file for suspicious entries:

    The hosts file is located at: C:\Windows\System32\drivers\etc\hosts

    Open it with Notepad (run as administrator)

Use a VPN to Bypass DNS Issues

If you suspect your ISP is having DNS issues or is blocking certain domains, using a VPN can help:

  • A VPN will route your DNS queries through its own servers
  • This can bypass DNS-based censorship or filtering
  • It can also help diagnose if the problem is with your ISP's DNS servers

Note: For more information on VPNs, see our What is a VPN? guide.

When to Contact Your ISP

If you've tried all the troubleshooting steps and still experience DNS issues, the problem might be with your Internet Service Provider. Contact your ISP's technical support if:

  • Multiple devices on your network have the same DNS issues
  • The problem persists after trying alternative DNS servers
  • You can connect to IP addresses directly but not to domain names
  • The issue started suddenly and affects all websites
  • Your neighbors with the same ISP are experiencing similar issues

Frequently Asked Questions (FAQ)

Remember: When you encounter a "DNS server not responding" error, DNS issues can often be resolved by simply restarting your router or clearing your DNS cache. Always try these simple steps first before attempting more complex solutions.