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October 3, 2025·Last updated on October 3, 2025
DNS errors can take your website offline in seconds. The statistics are alarming: 72% of organizations suffered a DNS attack in 2024 and almost half suffered from DNS hijacking. Attackers manipulate DNS queries to redirect users to malicious servers, creating major vulnerabilities.
When DNS is functioning properly, everything from email delivery to web browsing works smoothly. But DNS problems can lead to downtime, slow performance, failed connections, and even data leaks. These issues are often caused by simple misconfigurations, giving attackers exactly what they want.
In this guide, we’ll walk through 12 of the most common DNS problemsexplain which is causing the DNS errorsand share tips about how to fix DNS errors quickly. Whether you’re dealing with cryptic messages or unexplained glitches, this DNS troubleshooting reference will keep your site running smoothly.
This error means that a DNS lookup has failed entirely: the system could not find any IP addresses for the requested domain.
The label ‘NXDOMAIN’ stands for ‘Non-existing domain’. That could mean:
- A typo in the domain name
- An unregistered or expired domain
- Corrupted local DNS cache
- Wrong DNS server settings
- Conflicting VPN, antivirus, or firewall rules
- A misconfigured hosts file
- Chrome-specific flags interfering with DNS
This results in complete inaccessibility. Chrome shows ‘This site can’t be reached’, while Firefox shows ‘We’re having trouble finding that site’.
- Double check the domain name
- Flush DNS cache (ipconfig /flushdns on Windows, Terminal commands for macOS)
- Renew your IP address
- Switch to public DNS (e.g. 8.8.8.8 or 1.1.1.1)
- Check your hosts file
- Temporarily disable VPN/firewall
- Confirm that A records are present and pointing to a valid server
Unlike NXDOMAIN, SERVFAIL occurs when the DNS server cannot complete a valid query even though the domain exists.
- DNSSEC validation errors (expired or mismatched keys)
- Wrong zone file configurations
- Missing glue records
- Overloaded or offline authoritative name servers
- Excessive CNAME chains (recursive depth exceeded)
- Firewall or routing issues
Users and bots cannot access your site or send email. SERVFAIL is also harmful to SEO because search engines cannot crawl your domain consistently.
- Validate DNSSEC signatures
- Check and correct the syntax of zone files
- Check glue records and name server delegation
- Monitor server load and ensure redundancy
- Keep CNAME chains under eight entries
A REFUSED error means that the DNS server deliberately rejected your query.
- Access restrictions or security policies
- IP filtering or country-based blocking
- Unauthorized requests (e.g. zone transfers)
- Protocol mismatch (e.g. blocked TCP connections)
- Firewall rules or DNS server misconfigurations
This DNS problems cause inaccessibility of the website and service interruptions. Users may see “ERR_CONNECTION_REFUSED” and apps that rely on DNS will stop working.
- Flush your local DNS
- Switch to automatic or public DNS settings
- Testing with Google (8.8.8.8) or Cloudflare (1.1.1.1)
- Check firewall and port rules (UDP/TCP on port 53)
- Verify that your registrar and hosting provider have matching name servers
This occurs when the DNS query times out before receiving a response, often without a visible error code.
- Slow or overloaded DNS servers
- Bad routing paths or high latency
- DNS servers are located too far away geographically
- Blocked or filtered DNS traffic on your network
- Low-resource DNS resolvers
DNS timeouts often go unnoticed in logs but cause significant slowdowns. Google reports that the bounce rate increases dramatically when the page load time exceeds 3 to 5 seconds.
- Use multiple DNS servers for failover
- Choose optimized DNS services with low latency
- Monitor DNS response time with tools like DNSPerf
- Reduce TTLs to minimize wait times
- Consider using a CDN for geographically distributed resolution
If your MX records are misconfigured, your organization’s email may stop working altogether.
- MX records pointing to CNAMEs (which is invalid)
- Syntax errors or missing periods in hostnames
- Duplicate records or incorrect priority values
- Records pointing to decommissioned servers
- Unable to verify domain ownership
Bounced emails, spam flags and delivery failures, especially with providers like Gmail or Outlook that rely on strict DNS validation.
- Map MX records to A records (not CNAMEs)
- Use priority values appropriately (lowest = primary server)
- Confirm ownership via DNS TXT records
- Clean up outdated or duplicate entries
- Test configurations with MXToolbox
Reverse lookups (rDNS) point IPs back to domain names. They are essential for email trust and authentication.
- Missing PTR records
- Mismatched forward (A) and reverse (PTR) records
- Dynamic IPs without PTR setting
- Hosting providers that do not support custom rDNS
- Blacklisted IPs
- Ask your ISP or host to assign a valid PTR
- Use static IPs for outgoing email
- Make sure the A and PTR data match exactly
- Set up SPF, DKIM and DMARC for extra confidence
DNS changes do not apply immediately; it takes some time for them to spread worldwide.
- High TTL values (Time-to-Live).
- ISP level caching that you have no control over
- Global DNS root server delays
- Slow regional infrastructure
Users may see outdated content or receive bounced emails. It can also confuse search engines during site migrations.
- Reduce TTL to 300-600 seconds before scheduled changes
- Follow the progress with DNSChecker or WhatsMyDNS
- Clear local and browser DNS caches
- Consider CDN services to accelerate resolution
This broad category includes all the little bugs that silently break DNS behind the scenes.
- Typos in IP addresses
- Multiple CNAMEs assigned to one name
- Forward and backward mismatches
- Data still points to outdated infrastructure
This one quiet DNS problems can lead to man-in-the-middle attacks, downtime, or redirect errors.
- Check your DNS regularly
- Use a DNS provider that tracks changes and history
- Use dig or nslookup to manually validate records
- Implement DNS failover for important services
TTL settings determine how long records are kept in the cache by solvers. Longer values reduce load, but slow down updates.
- The default TTL remains at 86,400 seconds (24 hours)
- Do not lower TTL before major changes
- An attempt is being made to reduce the number of searches
High TTL means fast performance and low query costs, but DNS changes can take days to propagate.
Use 1800-3600s TTL for dynamic records and reduce it to 300s before migrations.
Open solvers respond to questions from everyone. That makes them vulnerable to DNS amplification and spoofing attacks.
- Misconfigured routers or firewalls
- DNS servers that allow unlimited recursion
- There are no ACLs (access control lists) in place
You may unknowingly participate in DDoS attacks or expose your infrastructure to poisoning.
- Disable recursion on public servers
- Apply IP-based restrictions
- Use response limit (RRL)
- Follow BCP 38 to avoid spoofed traffic
Old DNS records pointing to inactive servers or services can silently cause resolution errors or security risks.
- Poor DNS hygiene
- No cleanup after server decommissioning
- Lack of change management during infrastructure updates
Outdated records can be misused to take over subdomains or cause traffic to be routed to unintended destinations.
- Scheduled DNS audits
- DNS cleanup tools
- Manual review of critical mentions
- Retire workflows associated with DNS updates
Your authoritative name servers are the final source of truth. If they remain open, you risk a total domain compromise.
- Allow recursion on authoritative servers
- No firewall or ACLs on zone transfers
- No DNSSEC signing
From cache poisoning to DDoS, unsecured name servers open the door to widespread abuse.
- Disable recursion
- Restrict zone transmissions with TSIG
- Use DNSSEC to verify data integrity
- Placing primary files behind firewalls or as hidden masters
DNS errors can feel like a black box until they take your site offline or break your email system. But most DNS errors are preventable with proper installation and regular maintenance.
Understanding what causes DNS errors, performing consistent DNS troubleshooting, and knowing how to resolve DNS errors when they occur will give you control over one of the most critical layers of your digital infrastructure.
From slow searches to hijacked records, these common DNS problems you don’t have to be surprised. Bookmark this guide, check your information, and stay ahead of DNS issues before they impact your business.