DNS Monitoring: Catching Silent Failures

DNS: The Silent Point of Failure

DNS is the foundation of every web service. When DNS fails, everything fails—but DNS failures are often silent and intermittent. A misconfigured record might work for some users but not others. A propagation delay might resolve itself before you notice. DNS monitoring catches these invisible failures.

Common DNS Failure Modes

DNS can fail in subtle and dangerous ways.

Propagation Delays

After a DNS change, records propagate at different speeds across the internet. Some users see the new records immediately; others see cached records for hours. Monitor from multiple regions to detect propagation issues.

Record Hijacking

DNS hijacking redirects your domain to a malicious server. Regular DNS monitoring detects when your A, AAAA, or CNAME records change unexpectedly.

TTL Misconfiguration

Too-low TTL values increase DNS query volume and latency. Too-high TTL values make changes slow to propagate. Monitor your effective TTL values and adjust for your use case.

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Setting Up DNS Monitoring

FourSight's DNS monitoring queries your domain's records from multiple nameservers and compares results. Any discrepancy triggers an alert, catching hijacking, propagation issues, and misconfiguration.

DNS records to monitor:

A/AAAA records  → Your primary domain and API subdomains
CNAME records   → CDN and third-party service integrations
MX records      → Email delivery (monitor separately)
TXT records     → SPF, DKIM, domain verification

DNS Provider Redundancy

Single DNS provider failure can take down your entire infrastructure. Consider running secondary DNS with a different provider and monitoring both. FourSight can verify that records are consistent across providers.

💡 The 2021 Akamai DNS outage took down thousands of websites for hours. Companies using a secondary DNS provider were unaffected. DNS redundancy is cheap insurance.

DNSSEC Monitoring

If you've enabled DNSSEC, monitor that signatures are valid and refreshed. Expired DNSSEC signatures cause complete DNS resolution failure for DNSSEC-validating resolvers, which includes an increasing number of ISPs and enterprise networks.