FreeBSD 13 CARP Failover Not Triggering

📖 ~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

High-availability pairs on FreeBSD 13 depend on CARP and often pfsync to fail over predictably.

Environment & Reproduction

Backup node never becomes MASTER during primary failure, causing prolonged service outage.

Root Cause Analysis

Mismatched VHID secrets, blocked advertisement traffic, skew misconfiguration, or missing carp module.

Quick Triage

Use ifconfig carpX, tcpdump for proto carp, and verify pfsync/carp settings on both nodes.

Step-by-Step Diagnosis

Confirm both peers share identical VHID and password settings. image_ref=0

Solution – Primary Fix

Load carp module, correct rc.conf interface directives, adjust skew, and reload pf with pfsync allowances. image_ref=1

Solution – Alternative Approaches

Enable dependencies with sysrc and restart netif, routing, and pf services in controlled order.

Verification & Acceptance Criteria

Keep CARP and pfsync declarations version-controlled to avoid silent drift between peers.

Rollback Plan

Permit CARP protocol and pfsync traffic on sync interfaces; avoid filtering essential failover packets.

Prevention & Hardening

Simulate failover by withdrawing primary and confirm backup transitions to MASTER rapidly.

Related Errors & Cross-Refs

Track CARP state events and alert on split-brain or prolonged BACKUP state anomalies.

Related tutorial: View the step-by-step tutorial for freebsd-13.

View all freebsd-13 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Review man carp, man pfsync, and FreeBSD HA deployment documentation.