Ubuntu 20.04 DNS Resolution Fails Intermittently

📖 ~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

Web and package access fails due to inconsistent name resolution.

Environment & Reproduction

Ping by IP works while domain names fail or time out.

Root Cause Analysis

Ubuntu 20.04 systems using systemd-resolved and Netplan.

Quick Triage

Invalid upstream DNS settings, stale cache, or VPN override conflicts.

Step-by-Step Diagnosis

Use resolvectl query and inspect per-link DNS configuration.

Solution – Primary Fix

Set reliable DNS servers in Netplan, apply changes, and restart resolver.

Solution – Alternative Approaches

Repeated lookups succeed quickly across reboot and network reconnect.

Verification & Acceptance Criteria

Standardize DNS sources and avoid conflicting network profile overrides.

Rollback Plan

Escalate if upstream DNS provider outages are suspected.

Prevention & Hardening

Restore prior Netplan YAML and flush resolver caches.

Related Errors & Cross-Refs

systemd-resolved and Netplan official documentation.

Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.

View all Ubuntu 20.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Editing /etc/resolv.conf directly is temporary on systemd-resolved systems.