Sometimes you may need to upgrade devices by several versions, where a direct upgrade from current to desired version is not possible.
Using middle firmware means applying one or more firmware versions between the current version and the desired version during an upgrade sequence.
If you cannot go from firmware A to C without first installing B, then B is the middle firmware, and you must add two policies:
For instructions on setting up policies, see Apply a New Firmware Version to Multiple Devices.
Note that the device will usually reboot after the new firmware is received. Depending on the event triggers you specify in your policy, this upgrade sequence will therefore cause a minimum of two reboots.
We strongly recommend informing users if you have to apply a middle-firmware policy. This is because: