DNS Resolution Fails After NetworkManager Changes

📖 ~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

Hostnames fail to resolve while direct IP connectivity still works.

Environment & Reproduction

NetworkManager profile DNS values were overwritten or incorrect after interface updates.

Root Cause Analysis

Use nmcli connection show and cat /etc/resolv.conf to inspect active resolver state.

Quick Triage

Set explicit DNS with nmcli connection modify ipv4.dns ‘1.1.1.1 8.8.8.8’ ipv4.ignore-auto-dns yes.

Step-by-Step Diagnosis

Bring the connection down and up so NetworkManager rewrites resolver configuration.

Solution – Primary Fix

Test lookups using getent hosts and dig to confirm expected name resolution.

Solution – Alternative Approaches

Verify persistent DNS settings survive reboot and reconnection events.

Verification & Acceptance Criteria

Restore previous profile values from nmcli connection export backup or remove ignore-auto-dns.

Rollback Plan

Version-control nmcli profile changes and avoid manual edits to resolv.conf on managed systems.

Prevention & Hardening

Alert on resolver timeouts from application logs and synthetic DNS checks.

Related Errors & Cross-Refs

Enforce network profile DNS in Ansible nmcli tasks for stable server builds.

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

Consult nmcli and NetworkManager docs for DNS precedence and profile behavior on RHEL 9.