FreeBSD 13 – intermittent DNS resolution failures – Fix & Prevention

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Applications randomly fail name lookups, causing partial outages and difficult incident triage.

Environment & Reproduction

Often triggered by flaky upstream resolvers or packet drops to DNS servers.

cat /etc/resolv.conf
host example.com
dig +tries=1 +time=2 example.com

Root Cause Analysis

Unstable upstream responses, timeout settings, or firewall policies disrupt DNS query completion.

Quick Triage

Confirm if failures are network-wide or specific to one resolver.

drill example.com @8.8.8.8
drill example.com @1.1.1.1
netstat -s -p udp

Step-by-Step Diagnosis

Capture query traffic and compare response timing distributions.

tcpdump -ni em0 port 53
dig +trace example.com
route -n get 8.8.8.8

Solution – Primary Fix

Use reliable resolver set and tune timeout/retry behavior for workload profile.

cp -a /etc/resolv.conf /etc/resolv.conf.bak
printf 'nameserver 1.1.1.1
nameserver 8.8.8.8
options timeout:2 attempts:2
' > /etc/resolv.conf

Solution – Alternative Approaches

Deploy local caching resolver with health-checked upstream rotation.

Verification & Acceptance Criteria

Lookup latency and failure rate return to expected SLO.

for i in 1 2 3 4 5; do host example.com; done
service local_unbound status || true

Rollback Plan

Restore prior resolver config if new DNS path introduces policy conflicts.

cp /etc/resolv.conf.bak /etc/resolv.conf

Prevention & Hardening

Monitor DNS error budgets and keep at least two independent recursive resolvers configured.

Related Errors & Cross-Refs

Related to package fetch timeouts, TLS handshake failures, and intermittent API endpoint errors.

Related tutorial: View the step-by-step tutorial for freebsd-13.

View all freebsd-13 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

resolv.conf(5), drill(1), and FreeBSD resolver best practices.