| For testing purposes, FortiGate-500E v7.0.15, build0566, 231024 is used. - Confirm in both FortiGates if the override is disabled as follows:
show full sys ha - Confirm the hostname and serials in both FortiGates as follows:
get system status The collected information shows as follows (output truncated for better readability):
Hostname: Fortigate-A
FG-SERIALXXX_A
Primary
Priority 200
FortiGate-500E v7.0.15,build0566,231024 (GA.M)
Override disable
Mode: Active - Pasive
--------------------------
Hostaname: Fortigate-B
FG-SERIALXXX_B
Secondary
Priority 100
FortiGate-500E v7.0.15,build0566,231024 (GA.M)
Override disable
Mode: Active - Passive
Initial notes: - This procedure also works for Active-Active environment.
- A person must be on-site to be able to disconnect and reconnect cables to the devices.
- Perform a full backup of the Primary node (FortiGate-A).
Activity Summary: - Currently, FortiGate-B has too many checksum differences between different tables and is out of Sync.
- Perform a Restore on FortiGate-B.
- Load a Backup on FortiGate-B, edit it, add it to the cluster, and resynchronize the HA.
Procedure: - Make a full backup of FortiGate-A (Active FortiGate with serial terminal FG-SERIALXXX_A).
- Disconnect (all cables) from the HA secondary cluster member, the FortiGate-B. (Secondary FortiGate with serial terminal FG-SERIALXXX_B.)
- Leave only the FortiGate-A connected (Active FortiGate with serial terminal FG-SERIALXXX_A). This equipment will remain operational to avoid service affectation. See Figure 1:
Note: If the cables are not labeled, proceed to identify them to avoid confusion when reconnecting them later. - Work with the FortiGate that is disconnected from the HA, that is, FortiGate-B (Hardware with the Serial number FG-SERIALXXX_B).
- Log in to the FortiGate-B via the management port and get connected to the GUI.
- The backup made in the step 1 file should be located in the PC connected to the FortiGate-B. Choose and Load the Backup made in Step 1 to this FortiGate-B:
- Once the backup is loaded, the FortiGate will reboot.
- Log back into the GUI and Edit the Hostname and basic HA configuration as follows:
 Note: If there is no access to the secondary member through the GUI, these changes must be performed through the serial console connection, but first the configuration must be restored using a TFTP server. More information in the following technical document: Technical Tip: Restoring a config file from the CLI by using TFTP server - (Optional) Via CLI could be updated as follows:
config system global
set hostname Fortigate-B
end config system ha
set priority 100 <- Set the value to 100, originally 200.
end <- Save the changes. Check from the CLI that the changes have been accepted: show full system global | grep hostname <- FortiGate-B should be the hostname. show full system ha | grep priority <- 100 should be the Priority. - Once these configuration settings have been made and verification has been performed, physically connect the secondary device (FortiGate-B) to the HA cluster and wait for it to sync. See Figure 2:
 If the units DO NOT sync, open a ticket with support and call support for immediate assistance. For more information on how to troubleshoot a checksum mismatch on HA clusters, see Troubleshooting Tip: Troubleshooting a checksum mismatch in a FortiGate HA cluster. | 
