π ~1 min read
Table of contents
Symptom & Impact
Hostname lookups fail and outbound package and API calls break.
Environment & Reproduction
Often triggered by VPN changes, network updates, or DNS server drift.
Root Cause Analysis
Invalid upstream DNS settings or resolver state corruption causes failures.
Quick Triage
Test name resolution path and confirm current resolver status quickly.
Step-by-Step Diagnosis
Inspect resolver configuration and journal entries to identify failing hops.
Solution – Primary Fix
Set correct DNS servers and restart resolver service to apply clean state.
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Solution – Alternative Approaches
Apply temporary DNS directly on the interface for immediate restoration.
Verification & Acceptance Criteria
Internal and external domains resolve consistently across repeated tests.
Rollback Plan
Restore prior resolver configuration if replacement servers are unstable.
Prevention & Hardening
Template DNS settings and monitor resolver health with alerting.
Related Errors & Cross-Refs
Can overlap with proxy misconfiguration and split-DNS routing issues.
Related tutorial: View the step-by-step tutorial for debian-11.
View all debian-11 tutorials on the Tutorials Hub β
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Debian networking and systemd-resolved operational documentation.
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