π ~1 min read
Table of contents
Symptom & Impact
Applications experience random host lookup failures, causing API, repository, and service discovery interruptions.
Environment & Reproduction
Common on dual-NIC systems, VPN clients, or mixed resolver configurations with systemd-resolved and custom DNS settings.
Root Cause Analysis
Resolver priority conflicts, unreachable upstream nameservers, or stale resolver cache produce inconsistent query behavior.
Quick Triage
Check resolver status, test direct nameserver queries, and confirm routing to configured DNS endpoints.
Step-by-Step Diagnosis
Review netplan, resolved configuration, journal entries, and packet flow to identify failure domains.
Solution – Primary Fix
Align resolver sources, set reliable nameserver order, apply netplan updates, and restart resolver services.
Still having issues? Our IT Solutions & Services team can diagnose and resolve this for you. Get in touch for a free consultation.
Solution – Alternative Approaches
Deploy local caching DNS, pin interface DNS per route, or use managed DNS policy controls.
Verification & Acceptance Criteria
Repeated queries return stable answers with acceptable latency and no resolver timeout logs.
Rollback Plan
Reapply prior resolver files and netplan YAML, then restart networking if regressions appear.
Prevention & Hardening
Use immutable baseline resolver profiles and monitor DNS health via synthetic probes.
Related Errors & Cross-Refs
Related to TLS handshake failures and apt repository host resolution errors.
Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.
View all Ubuntu 20.04 LTS tutorials on the Tutorials Hub β
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Consult Ubuntu networking, netplan, and systemd-resolved administration references.
Need Expert Help?
If you cannot resolve this yourself, our team offers hands-on Server Management, Managed IT Services, and flexible Support Plans. Contact us today β we respond within one business day.
