RHEL 8 Static Routes Disappear After Reboot With NetworkManager

📖 ~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

Traffic to specific subnets fails after reboot because static routes are missing. Applications relying on backend networks time out, and failover logic may route traffic incorrectly.

Environment & Reproduction

Occurs on RHEL 8 hosts using manual ip route commands instead of NetworkManager profile settings. Reproduce by adding runtime routes, rebooting, and checking route tables.

Root Cause Analysis

Runtime route changes are ephemeral unless written into connection profiles or route files managed by NetworkManager. Conflicting DHCP options can also overwrite expected routing behavior.

Quick Triage

Use nmcli connection show, ip route, systemctl status NetworkManager, and journalctl -u NetworkManager to confirm whether routes are absent because of profile configuration.

Step-by-Step Diagnosis

Identify active connection profile, inspect ipv4.routes and ipv4.never-default settings, and compare post-boot route table to intended design. Check firewalld zones for interface mapping context.

Solution – Primary Fix

Persist routes with nmcli connection modify, reload the profile, and verify after reboot. Ensure systemctl-managed NetworkManager startup order is normal and no legacy scripts override route state.

Solution – Alternative Approaches

Use keyfile route definitions, Ansible-managed network roles, or centralized configuration management to enforce route consistency across fleet nodes.

Verification & Acceptance Criteria

Routes survive reboot, network tests to target subnets succeed, and journalctl shows clean profile activation without route overwrite warnings.

Rollback Plan

Restore prior connection profile, remove newly added route directives, and reactivate the old profile. Keep a console session ready to avoid management lockout.

Prevention & Hardening

Disallow ad-hoc runtime route changes in operations policy, template nmcli profiles, and continuously validate route tables against source-of-truth network design.

Related Errors & Cross-Refs

Related incidents include DHCP-provided default route takeover, DNS resolver drift, and firewalld zone mismatches tied to interface renaming.

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

Red Hat NetworkManager documentation, nmcli man pages, systemd networking startup references, and troubleshooting guidance using journalctl.