π ~1 min read
Table of contents
Symptom & Impact
Applications randomly fail to reach upstream services due to unreliable name lookups.
Environment & Reproduction
Seen on nodes with frequent resolver changes or split DNS environments.
Root Cause Analysis
Resolver cache and upstream policy mismatch can produce stale or failed responses intermittently.
Quick Triage
Verify /etc/resolv.conf target and current per-link DNS server assignments.
Step-by-Step Diagnosis
Collect resolver logs, cache stats, and compare behavior against direct upstream queries.
Solution – Primary Fix
Flush resolver cache, define stable DNS servers, and restart resolved cleanly.
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Solution – Alternative Approaches
Deploy local recursive resolver or disable caching for troubleshooting windows.
Verification & Acceptance Criteria
Repeated lookups return fast, consistent addresses with no resolver errors.
Rollback Plan
Revert resolved.conf and restart service if custom resolver policy causes regressions.
Prevention & Hardening
Track resolver health metrics and keep DNS topology changes under change control.
Related Errors & Cross-Refs
Related to temporary failure in name resolution and NXDOMAIN storms from stale cache.
Related tutorial: View the step-by-step tutorial for Debian 13.
View all Debian 13 tutorials on the Tutorials Hub β
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
systemd-resolved man pages and Debian DNS administration docs.
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