Both management boards and all of the FPCs in a FortiGate-6000 HA cluster run the same firmware image. You upgrade the firmware from the primary FortiGate-6000 management board.
session-pickup are enabled, firmware upgrades should only cause a minimal traffic interruption. Use the following command to enable these settings; they are disabled by default. These settings are synchronized.
config system ha
set uninterruptable-upgrade enable
set session-pickup enable
When these settings are enabled, the primary FortiGate-6000 management board uploads firmware to the backup FortiGate-6000 management board. The backup management board uploads the firmware to all of the FPCs in the backup FortiGate-6000. Then the management board and all of the FPCs in the backup FortiGate-6000 upgrade their firmware, reboot, and resynchronize.
Then all traffic fails over to the backup FortiGate-6000 which becomes the new primary FortiGate-6000. Then the management board and the FPCs in the new backup FortiGate-6000 upgrade their firmware and rejoin the cluster. Unless override is enabled, the new primary FortiGate-6000 continues to operate as the primary FortiGate-6000.
Normally you would want to enable
uninterruptable-upgrade to minimize traffic interruptions. But
uninterruptable-upgrade does not have to be enabled. In fact, if a traffic interruption is not going to cause any problems, you can disable
uninterruptable-upgrade so that the firmware upgrade process takes less time.
As well some firmware upgrades may not support
uninterruptable-upgrade. For example,
uninterruptable-upgrade may not be supported if the firmware upgrade also includes a DP3 processor firmware upgrade. Make sure to review the release notes before running a firmware upgrade to verify whether or not enabling
uninterruptable-upgrade is supported to upgrade to that version.