DNS (Domain Name System) is one of the most fundamental components of the internet, acting as a bridge between human-readable domain names (e.g., www.example.com) and machine-readable IP addresses (e.g., 192.0.2.1). Broken DNS records can significantly affect website availability, email deliverability, and overall network performance. Diagnosing and fixing DNS record issues is a critical skill for anyone managing a website, network, or online service.

In this guide, we’ll explore what DNS records are, how to troubleshoot broken DNS records, and provide step-by-step solutions for resolving common DNS errors. Whether you’re a system administrator or just a user trying to resolve DNS issues, this knowledgebase will equip you with the necessary tools and techniques.

What Are DNS Records?

DNS records are entries in a DNS database that tell DNS servers how to resolve domain names into IP addresses, and other domain-specific information like mail servers, subdomains, and more. Here are the most common types of DNS records:

1. A Record: Maps a domain name to an IPv4 address (e.g., example.com to 192.0.2.1).
2. AAAA Record: Maps a domain name to an IPv6 address.
3. MX Record: Specifies the mail servers for a domain, allowing emails to be delivered to the correct address.
4. CNAME Record: Alias record that points one domain to another (e.g., www.example.com to example.com).
5. TXT Record: Stores text data, commonly used for SPF, DKIM, and DMARC for email security.
6. NS Record: Specifies the authoritative name servers for a domain.
7. SRV Record: Defines the location (hostname and port) of servers for specific services (e.g., SIP, LDAP).
8. PTR Record: Reverse lookup record that maps an IP address to a domain name.

Common DNS Errors and Broken DNS Records

A broken DNS record can refer to a record that is either missing, misconfigured, or outdated. Broken DNS records often lead to the following issues:

• Website not loading: Users cannot access your website, as the domain name does not resolve to the correct IP address.
• Email deliverability issues: Emails are either delayed, marked as spam, or not delivered due to improper MX records.
• SSL/TLS errors: Misconfigured DNS settings can lead to SSL certificate errors if the domain doesn’t match the expected names in the certificate.
• Subdomain issues: If a CNAME or A record for a subdomain is broken, users won’t be able to access services hosted on those subdomains.

Some of the most common DNS errors include:

1. DNS_PROBE_FINISHED_NXDOMAIN: Domain not found or DNS resolution failure.
2. Server Not Found: Browser cannot find the server, indicating DNS resolution failure.
3. Incorrect MX Records: Email not being delivered because of broken or misconfigured MX records.
4. DNS Timeout: DNS queries take too long to return, resulting in timeouts.

How to Troubleshoot Broken DNS Records

To troubleshoot broken DNS records, follow a systematic approach to identify the root cause. The key steps in diagnosing and resolving DNS errors include:

Confirm DNS Record Configuration

The first step in troubleshooting broken DNS records is to confirm that the DNS records are correctly configured. This can be done by checking your domain’s DNS zone file.

How to Check DNS Records:

• Using Online Tools: Websites like MXToolbox, DNSstuff, and IntoDNS can check your DNS records for misconfigurations, missing records, and other issues.
• Using Command-Line Tools: You can use the following commands to check DNS records:
  • nslookup example.com – Returns the A record for the domain.
  • dig example.com – Provides detailed information about DNS records, including A, MX, TXT, and more.
  • whois example.com – Checks the authoritative name servers for the domain.

What to Look For:

• A Records: Make sure they point to the correct IP address for your website or service.
• MX Records: Verify that they point to the correct mail server. Double-check the priority of your mail servers.
• CNAME Records: Ensure that any subdomains correctly point to the right domain.
• TTL (Time-to-Live): Ensure the TTL values are appropriate. High TTL values may cause outdated records to persist in DNS caches.

Verify DNS Propagation

DNS changes can take some time to propagate across the globe. If you’ve recently made changes to your DNS records, the issue may be caused by DNS propagation delays.

How to Check DNS Propagation:

You can use tools like Whatsmydns to check if your DNS changes have propagated globally. This tool checks if your domain’s records are consistent across different DNS servers.

What to Do:

• Wait for DNS Propagation: DNS changes can take anywhere from a few minutes to 48 hours to fully propagate. During this time, some users may experience issues accessing your domain.
• Use Low TTL: When making changes to DNS records, set a low TTL (e.g., 300 seconds) to speed up propagation during updates.

Check for DNS Server Issues

If your DNS server is misconfigured or down, it may be unable to resolve domain names properly, leading to broken DNS records. DNS servers can fail due to incorrect settings, outages, or configuration changes.

How to Check DNS Server Health:

• Use ping or traceroute: Run ping or traceroute to check the availability of your DNS server. Example:

  ping 8.8.8.8  # Google's public DNS server
  traceroute 8.8.8.8
  

• Check for DNS Server Outages: Use websites like DownDetector to see if there are any known issues with DNS servers.

What to Do:

• Test Alternate DNS Servers: If you suspect the DNS server is down or slow, try switching to a public DNS service like Google DNS (8.8.8.8), Cloudflare DNS (1.1.1.1), or OpenDNS.
• Restart Your DNS Server: If you are managing your own DNS server, restart it to ensure that any configuration changes are properly applied.

Check for DNS Caching Issues

DNS caching can cause problems if outdated records are stored in local caches. DNS resolvers, operating systems, and browsers cache DNS information to speed up lookups, but this can lead to users seeing stale data.

How to Clear DNS Cache:

• Clear Browser Cache: Most browsers cache DNS records. Clear your browser’s cache to make sure it's not serving outdated records.
• Flush DNS Cache on Operating Systems:
  • Windows: ipconfig /flushdns
  • macOS: sudo killall -HUP mDNSResponder
  • Linux: sudo systemd-resolve --flush-caches

What to Do:

• Flush DNS Cache: On both the client-side (user’s machine) and DNS server-side, clear the cache to force a fresh DNS lookup.

Check for DNS Misconfigurations

Misconfigurations in DNS records, such as incorrect A, MX, or CNAME records, can break DNS resolution. Some common misconfigurations include:

• Incorrect A Records: Pointing to the wrong IP address.
• Incorrect MX Records: Email servers pointing to the wrong or non-existent mail servers.
• CNAME Conflicts: A subdomain being incorrectly aliased to the wrong domain or another record type (e.g., CNAME conflicting with an A record).

How to Fix Misconfigured DNS Records:

• Correct the Record: Edit your DNS records to ensure they point to the correct destination.
• Check for Conflicts: Make sure you don’t have conflicting records, such as a CNAME and A record for the same subdomain.
• Verify with Third-Party Services: If you're using a third-party service (like a CDN or email service), ensure their DNS instructions are correctly followed.

Step-by-Step Solutions to Common DNS Errors

DNS_PROBE_FINISHED_NXDOMAIN

This error occurs when the domain name cannot be resolved to an IP address.

Solution:

• Check DNS Configuration: Verify that the A record for the domain is configured correctly and that it points to the correct IP address.
• Check for Typos: Ensure there are no typos in the domain name.
• Flush DNS Cache: Clear your local DNS cache and try again.

Server Not Found

This error typically appears when a domain cannot

be resolved.

Solution:

• Check DNS Records: Use tools like dig or nslookup to confirm the A record is set correctly.
• Check DNS Server: If the DNS server is down or slow, switch to a public DNS service like Google DNS (8.8.8.8).

MX Record Issues (Email Not Delivered)

If your MX records are incorrect, emails will not be delivered.

Solution:

• Verify MX Records: Ensure that the MX records are pointing to the correct mail server addresses.
• Check Priority: Ensure the MX records have the correct priority and that they are not conflicting with other records.

SSL/TLS Certificate Errors

SSL/TLS errors occur when DNS records are misconfigured, causing a mismatch between the certificate and domain.

Solution:

• Ensure Correct A Record: Ensure the domain points to the correct server IP.
• Check CN and SAN Entries: Make sure the SSL certificate includes the domain name in its Common Name (CN) or Subject Alternative Name (SAN) fields.

Usage Field for Troubleshooting Broken DNS Records & Resolving Errors

Common Use Cases for DNS Troubleshooting:

1. Website Downtime or Inaccessibility:

   • When users cannot access a website due to DNS errors, troubleshooting is crucial to restore access. DNS misconfigurations like incorrect A or CNAME records often cause such issues.

2. Email Delivery Failures:

   • Broken MX (Mail Exchange) records can cause email delivery issues, such as emails bouncing back or being undelivered. Troubleshooting broken DNS records can help restore email functionality.

3. SSL/TLS Errors:

   • SSL certificate errors can arise if DNS records are not pointing to the correct server or if the server’s certificate doesn’t match the domain name due to DNS issues.

4. DNS Server Misconfiguration:

   • Organizations often experience DNS-related outages due to incorrect configurations at their DNS servers. These can affect internal network resolution, website availability, and email services.

5. DNS Propagation Delays:

   • After making DNS changes (like updating A records or switching nameservers), DNS propagation delays may cause users to experience intermittent access or outdated records. This needs to be diagnosed and resolved for consistency.

6. DNS Cache Problems:

   • DNS caching issues, either on the local machine or on DNS servers, can lead to outdated or incorrect DNS records being served. Clearing DNS cache can often resolve these problems.

7. Subdomain Misconfigurations:

   • Misconfigured CNAME or A records for subdomains can lead to failed connections to services hosted on subdomains. Troubleshooting is necessary to correct these configurations.

8. Reverse DNS Lookup Failures:

   • When reverse DNS (PTR) records are not properly configured, it may affect services like email (causing emails to be marked as spam) or networking services that rely on IP-to-hostname resolution.

9. DNS Resolver Failures:

   • A DNS resolver issue on the client-side (like on a local computer or within an organization's network) can prevent the correct resolution of domain names, leading to slow or failed connections.

10. Domain Configuration Changes:

    • When switching web hosting services, email providers, or CDN providers, troubleshooting DNS records and resolving errors ensures that new services are properly configured and accessible.

Technical Issues for Troubleshooting Broken DNS Records & Resolving Errors

Common Technical Issues:

1. DNS_PROBE_FINISHED_NXDOMAIN Error:

   • This error typically occurs when the domain name does not exist or cannot be resolved, often due to missing or incorrect DNS records (like A or CNAME records).

2. Server Not Found:

   • This happens when the DNS server fails to resolve the domain name, which may occur due to broken A records, DNS server issues, or misconfigured network settings.

3. Email Not Delivered (MX Record Issues):

   • Email delivery failures due to incorrect or missing MX records, which specify the mail servers responsible for handling emails for a domain.

4. Incorrect DNS Record Caching:

   • DNS cache, either on the local machine or DNS resolvers, can hold outdated or corrupted information, causing DNS resolution issues and leading to errors when accessing websites or sending emails.

5. TTL (Time-to-Live) Issues:

   • If DNS records are set to a high TTL value, changes to DNS records may not propagate quickly, causing delays in updating records and causing issues like inconsistent website access.

6. CNAME Conflicts:

   • Having a CNAME record pointing to a domain while also having an A record for the same subdomain can cause conflicts, leading to DNS resolution errors.

7. DNS Server Downtime:

   • If the authoritative DNS server for your domain is down or unreachable, it may prevent DNS records from being retrieved, causing websites or emails to fail.

8. DNS Resolver Errors:

   • A misconfigured or malfunctioning DNS resolver (e.g., a local DNS server or ISP's DNS server) may not be able to resolve domain names correctly.

9. Reverse DNS Lookup Failures:

   • If the PTR records for reverse DNS lookups are missing or incorrectly configured, it can result in services failing to authenticate or rejecting emails due to lack of domain validation.

10. DNS Propagation Delays:

    • Changes made to DNS records can take time to propagate across the internet. This delay can cause inconsistent results where some users see the new records, while others continue to access old configurations.

Technical FAQs for Troubleshooting Broken DNS Records & Resolving Errors

What is a DNS record, and why is it important?

Answer: DNS records are entries in a DNS database that define how domain names are resolved to IP addresses and other resources. Common DNS records include A records, MX records, CNAME records, and TXT records. They are essential for directing traffic to the correct servers for websites, email, and other services.

How can I check if my DNS records are correctly configured?

Answer: You can use tools like nslookup, dig, or online services like MXToolbox or DNSstuff to check the configuration of your DNS records. These tools will show you whether your DNS records (A, MX, CNAME, etc.) are correctly set up.

What is the DNS_PROBE_FINISHED_NXDOMAIN error, and how do I fix it?

Answer: This error occurs when the domain cannot be found in DNS records, often due to misconfigured or missing A or CNAME records. To fix it, check your DNS settings to ensure the domain has the correct A record and that no DNS propagation issues are delaying the update.

How do I troubleshoot email delivery issues caused by broken MX records?

Answer: Verify that the MX records are correctly configured in your DNS settings. Ensure they point to the correct mail server and that the priority settings are correct. Use tools like MXToolbox to check if the MX records are properly set up and if your mail server is reachable.

How do I clear DNS cache to resolve DNS resolution issues?

Answer: To clear your DNS cache:

• Windows: Open Command Prompt and type ipconfig /flushdns.
• macOS: Open Terminal and type sudo killall -HUP mDNSResponder.
• Linux: Run sudo systemd-resolve --flush-caches.

Clearing the cache ensures that outdated records are removed, allowing your device to fetch fresh DNS records.

How long does it take for DNS changes to propagate?

Answer: DNS changes typically take anywhere from a few minutes to 48 hours to fully propagate across the internet, depending on the TTL (Time-to-Live) values set for your DNS records. Lower TTL values speed up propagation.

How can I troubleshoot DNS server downtime or failures?

Answer: Test the availability of your DNS server using ping or traceroute. If the server is down or unreachable, check your DNS server’s logs, restart the DNS service, or try switching to a public DNS service like Google DNS (8.8.8.8).

How do I check for CNAME conflicts in my DNS records?

Answer: A CNAME record conflict occurs if you have both a CNAME and another record (like an A record) for the same subdomain. Check your DNS records to ensure there are no conflicting CNAME and A records for the same domain or subdomain. Correct the conflicting records to avoid resolution errors.

What should I do if my DNS server is slow to respond?

Answer: If your DNS server is slow, try switching to a faster public DNS server like Cloudflare DNS (1.1.1.1) or Google DNS (8.8.8.8). Alternatively, review your DNS server’s configuration and check for issues such as high traffic, outdated server software, or misconfigured network settings.

How can I fix reverse DNS lookup failures?

Answer: Reverse DNS (PTR) records must be correctly configured to match your IP address to the domain name. Ensure that the PTR records are set up with your IP provider or in your DNS configuration if you manage your own DNS server. Verify the reverse DNS record using tools like MXToolbox.