I have a ZTE modem at home. It works for itself and it works, but these modems have a “childhood disease” - when disconnected from the outlet, all settings are forgotten.
And now, after trying to collect all computer wires from under the table into one place, the modem had another “memory loss”.
After reading a little on the Internet, it became clear that the ZTE531B modem has the same stuffing as NetComm NB6Plus4W , respectively, the firmware should be suitable.
This firmware has more settings, DHCP support and dyndns.com



First, download the new firmware from the official site
Then tftp server (you can also have another one, but I used this one)
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Stitching:

0. Remember / write / take screenshots of settings;
1. Install the tftp server and in its settings enable “Transmit and Receive files”;
2. Unpack the firmware in the server's tftp file folder (by default, C: \ TFTP-Root);
2.1. You can rename the name of the firmware file to something shorter, so that it would be easier to write the name (I left just the version number - 363);
2.2. It does not hurt to disable various antiviruses and firewalls, you can also disconnect from the telephone line;
3. Start telnet (if it is necessary to enable telnet. How to do this, read on msdn ;
4. We write the command open <ip address of the modem> (I have this open 192.168.1.1);
4.1. Enter the username / password admin / admin (if it has not changed before);
4.2. We write the command tftp -g <tftp server ip address> -f <firmware name> -ti (I have this tftp -g 192.168.1.2 -f 363 -ti);
4.3. We are waiting for the modem to flash;
5. Reset the modem to the default settings (on the back of the machine, press the reset button for 10-30 seconds until the power button diode lights up in red);
6. Open the modem settings (write 192.168.1.1 in the browser, login / password: admin / admin);
7. Now we have NetComm NB6Plus4W.

Important! Wi-fi after the firmware will be turned off, so you need to flash through the wire.

This is how it looks like:

In the Internet after the firmware we want?

Now we need to configure the modem in the router mode, so that each time not to write a login and password when connecting to the Internet.
Open Quick start - Quick setup

VPI: 1
VCI: 50
click next
note PPPoE click next and again next
Now in the fields PPP username and PPP Password we write our username and password to connect to the Internet.
Click next to see DHCP enabled, again next and finish there.
In the menu Advanced - Internet - DNS server we remove the checkbox and register the DNS server. For stream it is: 212.188.4.10 and 195.34.32.116
Everywhere they write that Stream TV with DHCP does not work, it is not. Below I will write how to configure it.
Reboot the modem ( Management - reset router ).

Everything, the Internet should work.

And Stream TV?

Settings for TV are similar to Internet settings.
VPI: 1
VCI: 91
and
VPI: 1
VCI: 92
and instead of PPPoE we mark Bridge
Restart the modem again.

Configuring DHCP

Go to Advanced - Local network - DHCP server and write something like:



And now, how to make it all work with Stream-TV.

Open the Advanced - Port mapping .
Create a new group, call it as convenient. (I have tv)
Now we go into its properties and do as in the picture:


Everything, it remains only to restart the modem again and use it at your pleasure.

Based on stream-support.ru and own experience.
All this you do at your own peril and risk. I am not responsible for any damage to the equipment.