Extract Huawei E3531i-2 Firmware 21.521.31.00.356 on your computer
Install the Firmware update file for Huawei E3531i-2 downloaded from Huaweiflashfiles.com
Follow the procedure for updating Firmware that is given in Package.

Huawei Flash File | Size: 15.37 MB
Version: 21.521.31.00.356
Operator:Idea India
Operating systems: Windows 7/8/10/XP/Vista
Huawei E3531i-2 Firmware Download