📖 ~1 min read
Table of contents
Symptom & Impact
Random hostname resolution failures disrupt package installs, service discovery, and outbound API calls.
Environment & Reproduction
RHEL 8 typically relying on NetworkManager-managed /etc/resolv.conf with mixed DHCP and static profiles.
Root Cause Analysis
DNS servers are overwritten by competing profiles, invalid search domains, or unreachable resolvers.
Quick Triage
Inspect nmcli connection show, cat /etc/resolv.conf, and test with dig/nslookup against each configured resolver.
Step-by-Step Diagnosis
Review journalctl -u NetworkManager for DNS updates and link state changes.
Solution – Primary Fix
Set explicit DNS on active profile with nmcli connection modify ipv4.dns and ipv4.ignore-auto-dns yes; reconnect profile.
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Solution – Alternative Approaches
Run repeated dig queries and application connectivity checks to verify stable resolution.
Verification & Acceptance Criteria
Temporarily use known-good internal resolver list while investigating upstream DHCP or network policy issues.
Rollback Plan
Standardize DNS settings in network profiles and block unauthorized resolver overrides.
Prevention & Hardening
Use trusted internal resolvers and avoid public DNS where policy restricts data exfiltration risk.
Related Errors & Cross-Refs
Implement resolver health script that tests key zones and alerts on latency/failure spikes.
Related tutorial: View the step-by-step tutorial for rhel-8.
View all rhel-8 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
NetworkManager DNS settings docs, nmcli(1), and RHEL 8 networking troubleshooting references.
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