DNSSEC Errors: Complete Troubleshooting Guide

Troubleshooting Guide • Updated December 2024

DNSSEC errors can cause complete DNS resolution failures for your domain. This guide covers the most common DNSSEC errors, their causes, and step-by-step solutions to fix them.

Important: DNSSEC errors can make your website completely unreachable. If your site is down due to DNSSEC issues, the fastest fix is often to temporarily remove the DS record at your registrar.

Common DNSSEC Error Types

1. DNSSEC Validation Failed

This error occurs when a DNSSEC-validating resolver cannot verify the chain of trust for your domain.

Symptoms:

  • Website unreachable from DNSSEC-validating resolvers (Google DNS, Cloudflare DNS)
  • Works from non-validating resolvers
  • dig shows SERVFAIL with +dnssec flag

Causes:

  • DS record doesn't match DNSKEY
  • RRSIG signatures expired
  • Missing DNSKEY or RRSIG records

Solution: See our detailed guide: Fix DNSSEC Validation Failed

2. SERVFAIL Errors

SERVFAIL is the error returned when DNSSEC validation fails. The resolver refuses to return potentially spoofed data.

dig example.com +dnssec
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL

Quick Fix:

  1. Test without DNSSEC: dig example.com +cd (bypasses validation)
  2. If that works, DNSSEC is misconfigured
  3. Remove DS record at registrar to restore access immediately
  4. Fix the underlying issue, then re-add DS record

Full guide: SERVFAIL DNSSEC Troubleshooting

3. Expired DNSSEC Signatures

RRSIG records have expiration timestamps. If signatures expire, validation fails.

Check signature expiry:

dig example.com RRSIG +short

Look for the expiration date in the output. If it's in the past, signatures have expired.

Solution:

  • Automated DNSSEC (Cloudflare, Route 53) handles this automatically
  • For manual DNSSEC, re-sign your zone with fresh signatures
  • Consider switching to a managed DNSSEC provider

4. DS Record Mismatch

The DS record at your registrar must match the DNSKEY in your zone. Any mismatch breaks validation.

Verify DS record:

dig example.com DS +short     # DS at parent
dig example.com DNSKEY +short # Keys in zone

The DS digest should be a hash of the DNSKEY with key flag 257 (KSK).

Solution:

  1. Get the correct DS values from your DNS provider
  2. Update the DS record at your registrar
  3. Wait for propagation (up to 48 hours)

5. Chain of Trust Broken

DNSSEC requires an unbroken chain from root → TLD → domain. Any break causes validation failures.

Diagnose with DNSViz: Use DNSViz to visualize your DNSSEC chain and identify where it breaks.

DNSSEC Error Diagnostic Commands

# Check if DNSSEC is causing issues
dig example.com +dnssec      # Should show RRSIG records
dig example.com +cd          # Bypasses DNSSEC validation

# Check DS record
dig example.com DS @8.8.8.8

# Check DNSKEY
dig example.com DNSKEY

# Full DNSSEC trace
delv example.com @8.8.8.8

Emergency: Site Down Due to DNSSEC

If your website is completely unreachable due to DNSSEC errors:

  1. Remove DS record at registrar - This disables DNSSEC validation
  2. Wait 5-60 minutes for propagation
  3. Site should be accessible again
  4. Diagnose and fix the DNSSEC configuration
  5. Re-add DS record with correct values

Detailed guide: DNSSEC Breaking Your Site

Preventing DNSSEC Errors

  • Use managed DNSSEC: Providers like Cloudflare handle key rotation automatically
  • Monitor your domain: Set up alerts for DNSSEC validation failures
  • Test before going live: Verify DS records match before enabling DNSSEC
  • Document your setup: Keep records of key tags and algorithms used

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