Ubuntu 16.04 LTS DNS resolution fails intermittently on production hosts

📖 ~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 report random host lookup failures, causing API calls and package downloads to fail unpredictably.

Environment & Reproduction

Occurs on VMs using DHCP-provided resolvers with unstable upstream DNS paths.

Root Cause Analysis

Resolver settings are overwritten or upstream nameservers are unreachable under load or packet loss.

Quick Triage

Test each configured nameserver independently and verify route and firewall consistency.

Step-by-Step Diagnosis

Correlate lookup failures with DHCP lease events, interface resets, and resolvconf updates.

Solution – Primary Fix

Pin reliable resolver endpoints and adjust resolvconf or network manager policy to prevent drift.

Solution – Alternative Approaches

Deploy local caching resolver or route DNS through internal recursive servers.

Verification & Acceptance Criteria

Repeated dig and application probes succeed without timeout for sustained monitoring window.

Rollback Plan

Restore prior resolver template and DHCP client config if new policy causes regressions.

Prevention & Hardening

Use redundant DNS providers, monitor latency, and alert on resolver change events.

Related Errors & Cross-Refs

Temporary failure in name resolution, SERVFAIL bursts, and apt mirror lookup failures.

Related tutorial: View the step-by-step tutorial for Ubuntu 16.04 LTS.

View all Ubuntu 16.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu DNS troubleshooting, resolvconf behavior, and operational DNS reliability guidelines.