Intermittent DNS Resolution 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

Name lookups fail sporadically, affecting package downloads and external API calls.

Environment & Reproduction

Unreliable resolver order, DHCP overwrite, or upstream DNS packet loss.

Root Cause Analysis

Inspect nmcli device show and /etc/resolv.conf symlink target behavior.

Quick Triage

Run dig and getent hosts against each configured DNS server.

Step-by-Step Diagnosis

Set ipv4.dns and ipv4.ignore-auto-dns in nmcli profile to enforce known resolvers.

Solution – Primary Fix

Apply with nmcli connection down/up and validate stable query success.

Solution – Alternative Approaches

Check NetworkManager logs for DHCP renewals overriding DNS settings.

Verification & Acceptance Criteria

Ensure outbound UDP/TCP 53 is permitted in relevant zones.

Rollback Plan

Tune resolver options only after fixing primary infrastructure issues.

Prevention & Hardening

Application latency and error rates increase due to repeated lookup retries.

Related Errors & Cross-Refs

Use multiple internal DNS endpoints and monitor response latency.

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

Standardize DNS profile settings across RHEL 9 fleets via automation.