ZTE MF 823 (Megafon M100-3) 4G Modem
Device identification
Examine the output of lsusb. You should get:
$ Bus 002 Device 018: ID 19d2:1405 ZTE WCDMA Technologies MSM
Here are the modes for this modem:
1225 - Default mode. USB Mass Storage Device + CD-ROM + card reader.
1403 - Modem mode. RNDIS + Mass Storage Device.
1405 - CDC ethernet mode - the one we need
0016 - Download mode
If your modem does not appear as 19d2:1405 (or 1403), check USB 3G Modem#Mode switching arcticle.
Connection
This modem is recognized as Ethernet interface. That means you don't need special programs to work with it. Use NetworkManager or dhcdpc.
You will see that the LED (Blue - 2G/3G or Green - 4G) on modem is not blinking. To establish a connection, the following link (CGI command) should be entered in a browser:
http://192.168.0.1/goform/goform_set_cmd_process?goformId=CONNECT_NETWORK
To avoid entering this link every time, switch the modem to auto-connection mode:
If you are setting up internet using console (and therefore you have no browser), you should make request with referer, example:
curl --header "Referer: http://192.168.0.1/index.html" http://192.168.0.1/goform/goform_set_cmd_process?goformId=CONNECT_NETWORK
otherwise you'll get response {"result":"faulure"}
Commands
CGI command for 2G/3G/4G mode selection:
http://192.168.0.1/goform/goform_set_cmd_process?goformId=SET_BEARER_PREFERENCE&BearerPreference=
following options available after "=" sign (case-sensetive)
NETWORK_auto WCDMA_preferred GSM_preferred Only_GSM Only_WCDMA Only_LTE WCDMA_AND_GSM WCDMA_AND_LTE GSM_AND_LTE
This should be followed by the NETWORK CONNECT CGI command given before.
To switch the modem to FACTORY mode (WARNING! Unable to recieve further CGI commands, connection will be lost!), issue this link:
http://192.168.0.1/goform/goform_process?goformId=MODE_SWITCH&switchCmd=FACTORY
After switching to FACTORY mode you can issues commands via PuTTY:
putty /dev/ttyUSB0 AT+ZCDRUN=8 - switch to 1403 mode (RNDIS) AT+ZCDRUN=9 - switch to 1225 mode (default) AT+ZCDRUN=F - exit DOWNLOAD mode and switch to selected mode (RNDIS or default)
Telnet connection
The modem is available for telnet connection:
telnet 192.168.0.1 login: root password: zte9x15
As you can see, the modem has Linux system inside. You can even install some ARM-base packages (mc, nano...) or change something in Web-menu. Explore it carefully!
External links
Gsmforum.ru - ZTE MF823 thread (in Russian), check #7 thread for unlock instructions