Troubleshooting Tip: Resolving Active-Passive HA failure on FortiGate-6000 due to chassis ID conflict
| Description | This article describes how to resolve active-passive HA (High Availability) cluster formation issues on FortiGate-6000 when both units are configured with the same chassis ID. |
| Scope | FortiGate-6000 |
| Solution | Chassis IDs allow the FortiGate Clustering Protocol (FGCP) to identify each chassis. The chassis ID does not influence which unit becomes primary in the cluster. If both FortiGate-6000s in an active-passive cluster are configured with the same chassis ID, the following error appears in the logs: diagnose sys ha history read ----clipped--- <2025-09-22 05:42:01> vcluster-1: F6KF30T0199000XX is selected as the primary because it's the only member in the cluster. <2025-09-22 05:41:42> F6KF30T0199000XX failed to join because of chassis-id conflict 1. ---clipped--- When this occurs, both FortiGate-6000s begin operating in HA primary mode without forming a cluster. To resolve this issue:
config system ha set chassis-id 2 end
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