π ~1 min read
Table of contents
Symptom & Impact
Name resolution randomly fails, causing repository access problems and flaky application connectivity.
Environment & Reproduction
Seen on Ubuntu 18.04 with mixed static and DHCP DNS settings across changing interfaces.
Root Cause Analysis
Resolver ownership conflicts and stale resolv.conf content lead to unstable upstream DNS selection.
Quick Triage
Test queries against each configured nameserver to separate local resolver issues from upstream outages.
Step-by-Step Diagnosis
Check systemd-resolved state, inspect netplan/network config, and correlate failures with interface renewals.
Solution – Primary Fix
Standardize DNS source of truth, set explicit nameservers, restart resolver services, and flush cached entries.
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Solution – Alternative Approaches
Deploy a local caching resolver or split-DNS policy for hybrid corporate and public domains.
Verification & Acceptance Criteria
Repeated dig and application lookups remain stable through network restarts and lease renewals.
Rollback Plan
Restore previous network profile backups if new resolver ordering breaks internal routing.
Prevention & Hardening
Use configuration management and DNS drift alerts to prevent manual resolver changes.
Related Errors & Cross-Refs
Cross-reference apt host lookup failures and VPN split-DNS conflicts on Ubuntu 18.04.
Related tutorial: View the step-by-step tutorial for Ubuntu 18.04 LTS.
View all Ubuntu 18.04 LTS tutorials on the Tutorials Hub β
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
See Ubuntu network docs, systemd-resolved references, and enterprise DNS operations guides.
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