DNS Resolution Fails on RHEL 9 Servers

📖 ~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

Hosts cannot resolve internal or external domains, breaking package updates and service calls.

Environment & Reproduction

Use resolvectl status, nmcli dev show, and dig queries to validate resolver configuration and reachability.

Root Cause Analysis

Incorrect DNS servers in NetworkManager profile or blocked outbound DNS traffic.

Quick Triage

Set correct DNS via nmcli connection modify, reactivate connection, and verify /etc/resolv.conf behavior.

Step-by-Step Diagnosis

Capture failing lookup examples and current resolver source before modification.

Solution – Primary Fix

dig and getent hosts return valid records with low query latency.

Solution – Alternative Approaches

Test application dependencies and dnf operations that previously failed due to DNS errors.

Verification & Acceptance Criteria

Define resilient resolver pairs and monitor DNS health from server segments.

Rollback Plan

Revert to previous DNS settings if new resolver pair degrades service discovery.

Prevention & Hardening

Template NetworkManager DNS settings per site and role using automation.

Related Errors & Cross-Refs

Check journalctl -u NetworkManager and resolver-specific diagnostics.

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 nmcli profile output, query failures, and firewall egress policy details.