📖 ~1 min read
Table of contents
Symptom & Impact
Hosts running RHEL 9 resolve domains incorrectly because NetworkManager profile DNS values are wrong.
Environment & Reproduction
Internal hostnames fail, resolver order is unexpected, or /etc/resolv.conf changes after reconnect.
Root Cause Analysis
DHCP-provided DNS overrides static settings, or an outdated connection profile is still active.
Quick Triage
Use nmcli to identify active connections and inspect ipv4.dns, ipv4.ignore-auto-dns, and search domains.
Step-by-Step Diagnosis
Set desired DNS values with nmcli and disable automatic DNS where policy requires static resolvers.
Solution – Primary Fix
Bring the profile down/up or restart NetworkManager, then verify resolver output and query success.
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Solution – Alternative Approaches
Confirm interaction with systemd-resolved if enabled, including domain routing behavior per interface.
Verification & Acceptance Criteria
Ensure firewalld and upstream ACLs allow UDP/TCP DNS traffic to configured resolvers.
Rollback Plan
SELinux typically does not alter DNS profile values, but audit denials if custom resolver daemons are used.
Prevention & Hardening
Inspect ‘journalctl -u NetworkManager –no-pager -n 100’ for profile override and DHCP option events.
Related Errors & Cross-Refs
Test with dig or getent hosts for both internal and external names after applying profile changes.
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 nmcli profile templates and enforce expected DNS settings via automation.
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