Air-ct2500-k9-2-0-0-0-fus.aes -

Unlike a standard AireOS firmware update (which changes the operating system features), an FUS updates the —specifically the bootloader and the PowerPC boot code .

If you’ve recently downloaded firmware for a Cisco 2500 Series Wireless Controller and noticed a file named air-ct2500-k9-2-0-0-0-fus.aes , you might be confused. You expected a .aes extension, but you need a .bin or .img file for an upgrade. air-ct2500-k9-2-0-0-0-fus.aes

Don’t panic. You haven’t downloaded the wrong file. You’ve just encountered Cisco’s . Unlike a standard AireOS firmware update (which changes