12 Critical DNS Errors That Can Break Your Website (+ Quick Fixes)

DNS errors can take your web site offline in seconds. The statistics are alarming: 72% of organizations suffered a DNS assault in 2024 and nearly half suffered from DNS hijacking. Attackers manipulate DNS queries to redirect customers to malicious servers, creating main vulnerabilities.

When DNS is functioning correctly, all the things from electronic mail supply to net shopping works easily. However DNS issues can result in downtime, sluggish efficiency, failed connections, and even knowledge leaks. These points are sometimes attributable to easy misconfigurations, giving attackers precisely what they need.

On this information, we’ll stroll via 12 of essentially the most widespread DNS issuesclarify which is inflicting the DNS errorsand share tips on methods to repair DNS errors shortly. Whether or not you are coping with cryptic messages or unexplained glitches, this DNS troubleshooting reference will maintain your web site operating easily.

This error signifies that a DNS lookup has failed totally: the system couldn’t discover any IP addresses for the requested area.

The label ‘NXDOMAIN’ stands for ‘Non-existing area’. That might imply:

• A typo within the area identify
• An unregistered or expired area
• Corrupted native DNS cache
• Mistaken DNS server settings
• Conflicting VPN, antivirus, or firewall guidelines
• A misconfigured hosts file
• Chrome-specific flags interfering with DNS

This ends in full inaccessibility. Chrome exhibits ‘This web site cannot be reached’, whereas Firefox exhibits ‘We’re having hassle discovering that web site’.

• Double verify the area identify
• Flush DNS cache (ipconfig /flushdns on Home windows, Terminal instructions for macOS)
• Renew your IP handle
• Change to public DNS (e.g. 8.8.8.8 or 1.1.1.1)
• Examine your hosts file
• Briefly disable VPN/firewall
• Verify that A information are current and pointing to a sound server

Not like NXDOMAIN, SERVFAIL happens when the DNS server can’t full a sound question though the area exists.

• DNSSEC validation errors (expired or mismatched keys)
• Mistaken zone file configurations
• Lacking glue information
• Overloaded or offline authoritative identify servers
• Extreme CNAME chains (recursive depth exceeded)
• Firewall or routing points

Customers and bots can’t entry your web site or ship electronic mail. SERVFAIL can be dangerous to search engine optimization as a result of serps can’t crawl your area constantly.

• Validate DNSSEC signatures
• Examine and proper the syntax of zone recordsdata
• Examine glue information and identify server delegation
• Monitor server load and guarantee redundancy
• Maintain CNAME chains below eight entries

A REFUSED error signifies that the DNS server intentionally rejected your question.

• Entry restrictions or safety insurance policies
• IP filtering or country-based blocking
• Unauthorized requests (e.g. zone transfers)
• Protocol mismatch (e.g. blocked TCP connections)
• Firewall guidelines or DNS server misconfigurations

This DNS issues trigger inaccessibility of the web site and repair interruptions. Customers may even see “ERR_CONNECTION_REFUSED” and apps that depend on DNS will cease working.

• Flush your native DNS
• Change to computerized or public DNS settings
• Testing with Google (8.8.8.8) or Cloudflare (1.1.1.1)
• Examine firewall and port guidelines (UDP/TCP on port 53)
• Confirm that your registrar and internet hosting supplier have matching identify servers

This happens when the DNS question occasions out earlier than receiving a response, typically and not using a seen error code.

• Gradual or overloaded DNS servers
• Dangerous routing paths or excessive latency
• DNS servers are situated too distant geographically
• Blocked or filtered DNS site visitors in your community
• Low-resource DNS resolvers

DNS timeouts typically go unnoticed in logs however trigger vital slowdowns. Google reviews that the bounce fee will increase dramatically when the web page load time exceeds 3 to five seconds.

• Use a number of DNS servers for failover
• Select optimized DNS providers with low latency
• Monitor DNS response time with instruments like DNSPerf
• Scale back TTLs to attenuate wait occasions
• Think about using a CDN for geographically distributed decision

In case your MX information are misconfigured, your group’s electronic mail could cease working altogether.

• MX information pointing to CNAMEs (which is invalid)
• Syntax errors or lacking durations in hostnames
• Duplicate information or incorrect precedence values
• Information pointing to decommissioned servers
• Unable to confirm area possession

Bounced emails, spam flags and supply failures, particularly with suppliers like Gmail or Outlook that depend on strict DNS validation.

• Map MX information to A information (not CNAMEs)
• Use precedence values ​​appropriately (lowest = main server)
• Verify possession through DNS TXT information
• Clear up outdated or duplicate entries
• Check configurations with MXToolbox

Reverse lookups (rDNS) level IPs again to domains. They’re important for electronic mail belief and authentication.

• Lacking PTR information
• Mismatched ahead (A) and reverse (PTR) information
• Dynamic IPs with out PTR setting
• Internet hosting suppliers that don’t help customized rDNS
• Blacklisted IPs

• Ask your ISP or host to assign a sound PTR
• Use static IPs for outgoing electronic mail
• Be certain the A and PTR knowledge match precisely
• Arrange SPF, DKIM and DMARC for additional confidence

DNS modifications don’t apply instantly; it takes a while for them to unfold worldwide.

• Excessive TTL values ​​(Time-to-Reside).
• ISP stage caching that you don’t have any management over
• World DNS root server delays
• Gradual regional infrastructure

Customers may even see outdated content material or obtain bounced emails. It may additionally confuse serps throughout web site migrations.

• Scale back TTL to 300-600 seconds earlier than scheduled modifications
• Comply with the progress with DNSChecker or WhatsMyDNS
• Clear native and browser DNS caches
• Take into account CDN providers to speed up decision

This broad class contains all of the little bugs that silently break DNS behind the scenes.

• Typos in IP addresses
• A number of CNAMEs assigned to 1 identify
• Ahead and backward mismatches
• Information nonetheless factors to outdated infrastructure

This one quiet DNS issues can result in man-in-the-middle assaults, downtime, or redirect errors.

• Examine your DNS usually
• Use a DNS supplier that tracks modifications and historical past
• Use dig or nslookup to manually validate information
• Implement DNS failover for necessary providers

TTL settings decide how lengthy information are saved within the cache by solvers. Longer values ​​scale back load, however decelerate updates.

• The default TTL stays at 86,400 seconds (24 hours)
• Don’t decrease TTL earlier than main modifications
• An try is being made to scale back the variety of searches

Excessive TTL means quick efficiency and low question prices, however DNS modifications can take days to propagate.

Use 1800-3600s TTL for dynamic information and scale back it to 300s earlier than migrations.

Open solvers reply to questions from everybody. That makes them weak to DNS amplification and spoofing assaults.

• Misconfigured routers or firewalls
• DNS servers that permit limitless recursion
• There are not any ACLs (entry management lists) in place

It’s possible you’ll unknowingly take part in DDoS assaults or expose your infrastructure to poisoning.

• Disable recursion on public servers
• Apply IP-based restrictions
• Use response restrict (RRL)
• Comply with BCP 38 to keep away from spoofed site visitors

Previous DNS information pointing to inactive servers or providers can silently trigger decision errors or safety dangers.

• Poor DNS hygiene
• No cleanup after server decommissioning
• Lack of change administration throughout infrastructure updates

Outdated information might be misused to take over subdomains or trigger site visitors to be routed to unintended locations.

• Scheduled DNS audits
• DNS cleanup instruments
• Guide evaluate of crucial mentions
• Retire workflows related to DNS updates

Your authoritative identify servers are the ultimate supply of fact. If they continue to be open, you danger a complete area compromise.

• Permit recursion on authoritative servers
• No firewall or ACLs on zone transfers
• No DNSSEC signing

From cache poisoning to DDoS, unsecured identify servers open the door to widespread abuse.

• Disable recursion
• Prohibit zone transmissions with TSIG
• Use DNSSEC to confirm knowledge integrity
• Inserting main recordsdata behind firewalls or as hidden masters

DNS errors can really feel like a black field till they take your web site offline or break your electronic mail system. However most DNS errors are preventable with correct set up and common upkeep.

Understanding what causes DNS errors, performing constant DNS troubleshooting, and understanding methods to resolve DNS errors after they happen gives you management over one of the vital crucial layers of your digital infrastructure.

From sluggish searches to hijacked information, these widespread DNS issues you do not have to be shocked. Bookmark this information, verify your info, and keep forward of DNS points earlier than they affect your enterprise.