Upgrading cluster firmware
You can upgrade the FortiOS firmware running on an HA cluster in the same manner as upgrading the firmware running on a standalone FortiGate unit. During a normal firmware upgrade, the cluster upgrades the primary unit and all subordinate units to run the new firmware image. The firmware upgrade takes place without interrupting communication through the cluster.
Upgrading cluster firmware to a new major release (for example upgrading from 5.0 MRx to 5.2.2) is supported for clusters. Make sure you are taking an upgrade path described in the release notes. Even so you should back up your configuration and only perform such a firmware upgrade during a maintenance window.
To upgrade the firmware without interrupting communication through the cluster, the cluster goes through a series of steps that involve first upgrading the firmware running on the subordinate units, then making one of the subordinate units the primary unit, and finally upgrading the firmware on the former primary unit. These steps are transparent to the user and the network, but depending upon your HA configuration may result in the cluster selecting a new primary unit.
The following sequence describes in detail the steps the cluster goes through during a firmware upgrade and how different HA configuration settings may affect the outcome.
1. The administrator uploads a new firmware image from the web-based manager or CLI.
2. If the cluster is operating in active-active mode load balancing is turned off.
3. The cluster upgrades the firmware running on all of the subordinate units.
4. Once the subordinate units have been upgraded, a new primary unit is selected.
This primary unit will be running the new upgraded firmware.
5. The cluster now upgrades the firmware of the former primary unit.
If the age of the new primary unit is more than 300 seconds (5 minutes) greater than the age of all other cluster units, the new primary unit continues to operate as the primary unit.
This is the intended behavior but does not usually occur because the age difference of the cluster units is usually less than the cluster age difference margin of 300 seconds. So instead, the cluster negotiates again to select a primary unit as described in An introduction to the FGCP on page 1310.
You can keep the cluster from negotiating again by reducing the cluster age difference margin using the ha-uptime-diff-margin option. However, you should be cautious when reducing the age or other problems may occur. For information about the cluster age difference margin, see An introduction to the FGCP on page 1310. For more information about changing the cluster age margin, see An introduction to the FGCP on page 1310.
6. If the cluster is operating in active-active mode, load balancing is turned back on.
Changing how the cluster processes firmware upgrades
By default cluster firmware upgrades proceed as uninterruptable upgrades that do not interrupt traffic flow. If required, you can use the following CLI command to change how the cluster handles firmware upgrades. You might want to change this setting if you are finding uninterruptable upgrades take too much time.
config system ha
set uninterruptible-upgrade disable
uninterruptible-upgrade is enabled by default. If you disable uninterruptible-upgrade the cluster still upgrades the firmware on all cluster units, but all cluster units are upgraded at once; which takes less time but interrupts communication through the cluster.
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