Intermittent DNS Resolution Failures On RHEL 9

📖 ~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

Name lookups randomly fail while direct IP connectivity still works.

Environment & Reproduction

Test with `dig`, `resolvectl query`, and `nmcli device show` to inspect active DNS servers.

Root Cause Analysis

Confirm resolver-related packages and NetworkManager plugins are present via dnf.

Quick Triage

Check `systemctl status NetworkManager` and any local caching resolver service units.

Step-by-Step Diagnosis

Use `journalctl -u NetworkManager –since -2h` for DNS update race or timeout messages.

Solution – Primary Fix

Capture effective `/etc/resolv.conf` management mode and profile DNS settings.

Solution – Alternative Approaches

Verify UDP/TCP 53 path and firewall policy between host and DNS servers.

Verification & Acceptance Criteria

Review AVC denials if local DNS proxy processes fail to read config or bind sockets.

Rollback Plan

Pin stable DNS servers in connection profile and restart affected network services.

Prevention & Hardening

Run repeated lookup loop tests and confirm no timeout spikes.

Related Errors & Cross-Refs

Deploy redundant resolvers and monitor DNS latency with service-level alerts.

Related tutorial: View the step-by-step tutorial for rhel-9.

View all rhel-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Provide packet captures, resolver logs, and profile exports for analysis.