Ubuntu 16.04 LTS – DNS resolution intermittently fails on servers – 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 fail to resolve hostnames intermittently, causing request retries and outages.

Environment & Reproduction

Appears under variable network conditions or unreliable upstream resolver paths.

Root Cause Analysis

Resolver misconfiguration, unstable upstream DNS, or stale cache states create failures.

Quick Triage

Validate resolver reachability and compare lookup behavior across nameservers.

Step-by-Step Diagnosis

Inspect resolver config, test latency, and capture failing lookup patterns.

Solution – Primary Fix

Pin stable resolvers, correct configuration files, and restart networking components.

Solution – Alternative Approaches

Deploy local caching resolver and route DNS via highly available internal services.

Verification & Acceptance Criteria

Name lookups succeed consistently and application error rate returns to baseline.

Rollback Plan

Revert resolver changes and restore previous DNS paths if regressions occur.

Prevention & Hardening

Add DNS health checks, redundant resolvers, and config drift monitoring.

Related Errors & Cross-Refs

Can overlap with transient network drops and SSL handshake 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 and resolver configuration documentation with operational best practices.