Standard firmware on the B311221 assumes you are plugged into a wall socket permanently in one location. Portable firmware changes the router's behavioral logic. Here is what portable firmware typically unlocks:
The B311-221 supports a hardware-based rollback; holding the WPS and Power buttons reverts the device to a previous firmware version if a new update fails or is incompatible with mods. Key Specifications for Portable Use huawei b311221 firmware portable