First, look at the device version from the box or the back of the modem, which is opposite to the serial number, then download the software from www.netis-systems.com.
(Note that the same version of the device will be downloaded and updated, for example, if your modem R123 … is version 1.
If 4311EU ……. V3 is download version 3. Otherwise, the device is out of warranty.)
Then, in the modem console, select the Maintenance section in the upgrade section of the downloaded file