HA Checksum Divergence on FortiGate 100F / 200F Active-Passive Clusters
Active-Passive High Availability clusters on FortiGate 100F, 101F, 200F, and 201F fail configuration synchronization due to checksum calculation divergence in ha_calc_config_checksum, leaving the secondary unit in an out-of-sync state and risking split-brain network failures during failover.
Technical Root Cause Analysis
FortiOS FGCP clusters continuously compute 128-bit CRC configuration hashes across every virtual domain to verify that primary and secondary units maintain identical security policies, interfaces, and system settings.
Under FortiOS 7.2.4–7.2.7 and 7.4.1–7.4.3 on middle-enterprise platforms (FG-100F / FG-200F series), the checksum engine ha_calc_config_checksum() incorporates non-canonical object references when hashing vpn certificate local and dynamically assigned FortiGuard certificate bundles. Because internal memory object pointers and certificate enrollment timestamps differ between physical units, the resulting SHA/CRC hash diverges. The HA management daemon detects the disparity and immediately halts incremental configuration synchronization to protect the primary configuration from corruption.
Affected Firmware & Blast Radius Matrix
| FortiOS Branch | Vulnerable Builds | Confirmed Clean Build | Status & Workaround |
|---|---|---|---|
| FortiOS 7.2 | 7.2.4 – 7.2.7 | 7.2.8+ | Recalculate checksums; force manual object sync |
| FortiOS 7.4 | 7.4.1 – 7.4.3 | 7.4.4+ | Upgrade to 7.4.4 GA with normalized hash parser |
| FortiOS 7.0 | Not Affected | 7.0 Branch Clean | Legacy certificate object serializer in 7.0 |
Platform Impact: High-density deployment impact on FortiGate 100F, 101F, 200F, and 201F active-passive HA clusters operating with deep SSL inspection and local factory certificates.
Step 01: Free Verification CLI (Safe Read-Only)
Execute these diagnostic commands on the primary cluster member to confirm checksum divergence and pinpoint the exact desynchronized sub-tables:
Diagnostic Commands
# 1. Inspect cluster-wide configuration checksum values across all members
diagnose sys ha checksum cluster
# 2. Pinpoint exact configuration difference tree for root VDOM
diagnose sys ha checksum diff root
# 3. Verify HA cluster status, uptime, and sync state flags
diagnose sys ha status
# 4. Check whether HA sync daemon is currently throttled or halted
diagnose sys ha dump-by vclusterRemediation & Workaround Steps (Teaser Preview)
Follow the complete step-by-step remediation guide in the Ferrite interactive platform:
Frequently Asked Questions
In affected builds, the configuration checksum calculation routine ha_calc_config_checksum incorporates internal pointer metadata from factory default certificates and dynamic VPN store handles. Because pointer addresses differ across nodes, the resulting CRC32 digests diverge, causing the cluster to report out-of-sync status even when plaintext configurations are 100% identical.
While active traffic continues to forward across the primary node, an out-of-sync cluster halts automatic incremental configuration synchronization. Any firewall policy or routing updates made on the primary will not propagate to the secondary, leading to catastrophic traffic loss or session blackholing if an unplanned failover occurs.
FortiOS 7.2.8 and FortiOS 7.4.4 permanently fix the defect by standardizing the canonical serialization format used by ha_calc_config_checksum, omitting volatile memory pointers from checksum calculations.