🟡 Medium   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: FreeBSD 12

📖 ~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

Configured VLAN interface comes up without expected IP after reboot, interrupting segmented network access.

Environment & Reproduction

Manual ifconfig commands work temporarily, but settings disappear after restart or interface bounce.

Root Cause Analysis

Incorrect cloned_interfaces order, missing ifconfig_ entries, or parent interface naming changes usually cause this.

Quick Triage

Inspect rc.conf with sysrc, check dmesg for NIC renaming, and confirm VLAN tag and parent interface mapping.

Step-by-Step Diagnosis

Validate boot-time interface creation sequence and ensure all VLAN variables are present in rc.conf. image_ref=0

Illustrative mockup for freebsd-12 — terminal_or_shell
Checking VLAN interface state with ifconfig — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Set cloned_interfaces and ifconfig_ values via sysrc, then restart netif and routing services. image_ref=1

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Illustrative mockup for freebsd-12 — log_or_config
Reviewing rc.conf VLAN definitions and parent interface settings — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Use devd or orchestration scripts only when static rc.conf definitions cannot model required dynamic behavior.

Verification & Acceptance Criteria

VLAN interface retains IP and connectivity after reboot, and route table reflects intended network segmentation.

Rollback Plan

Restore prior rc.conf network block and restart netif if new VLAN configuration causes outage.

Prevention & Hardening

Document interface naming conventions and validate network boot config in pre-maintenance checks.

May appear with duplicate route entries, ARP confusion, and switch trunk misconfiguration.

Related tutorial: View the step-by-step tutorial for freebsd-12.

View all freebsd-12 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Consult man rc.conf, man ifconfig, and FreeBSD VLAN network configuration examples.

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