DNS resolution intermittently fails

📖 ~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

External API calls and yum operations fail intermittently due to name resolution errors.

Environment & Reproduction

On RHEL 7 VMs, repeated dig and curl tests show random SERVFAIL or timeout responses.

Root Cause Analysis

Unreliable upstream DNS, incorrect search domain order, or resolv.conf overwritten by DHCP.

Quick Triage

Check /etc/resolv.conf, run dig @dns-server hostname, and compare success rates across servers.

Step-by-Step Diagnosis

Collect resolver timing with dig +stats, inspect NetworkManager hooks, and review journalctl for DHCP updates.

Solution – Primary Fix

Set reliable nameserver list, correct options timeout/attempts, and persist settings via network scripts.

Solution – Alternative Approaches

Deploy local caching resolver like dnsmasq and point hosts to internal DNS VIP.

Verification & Acceptance Criteria

100 consecutive dig queries succeed and application logs show no DNS-related failures.

Rollback Plan

Restore original resolver file and DHCP client settings if service dependency breaks.

Prevention & Hardening

Monitor DNS latency and configure redundant resolvers across availability zones.

Related Errors & Cross-Refs

Temporary failure in name resolution, Name or service not known, curl#6.

Related tutorial: View the step-by-step tutorial for rhel-7.

View all rhel-7 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

resolv.conf man page, RHEL DNS client configuration docs, dig troubleshooting guide.