Hello everyone. I'm using rb951ui-2hnd (firmware v6.18) with 3G modem Huawei E3131. After inserting this modem in usb port LTE interface is automatically created. As I understood, LTE or ppp-out interface creating depends on 3G modem versions - old one have ppp-out and almost all new HiLink modems have LTE mode. Is it right? Are there any other dependencies?
My problem is, that with LTE interface I get dynamic private IP address for this interface. And 3G modem itself has a real Internet address. So, I can't connect to Mikrotik outside. Besides, this also creates load problems - as 3G modem works as router. I think, setting it up in bridge mode with ppp-out interface will unload modem itselt.
So, my question is - is there any way to set up new LTE-interfaced modem in bridge mode and use ppp-out connection on Mikrotik? Or I just should use old one?

Have you added a DHCP client to the LTE interface and have masquerading turned on?
I'm not sure what you mean when you say 3G modems works as a router and it "unload modem itself".
LTE and PPP connection to a USB modem work pretty much the same.

Have you added a DHCP client to the LTE interface and have masquerading turned on?
I'm not sure what you mean when you say 3G modems works as a router and it "unload modem itself".
LTE and PPP connection to a USB modem work pretty much the same.

Yes, I have. Everything works. My question is about using 3G modem as bridge not as router. As I understood, with PPP mode we have ppp connection from Mikrotik itself. With LTE mode connection is established from 3G modem. LTE interface receives private ip address from 3G modem and uses it as default gateway. In that mode 3G modem works as router and does all the job for traffic routing and NATing which has an impact of its perfomance.

My question is about using 3G modem as bridge not as router

I am wondering about same thing now and found this topic abandoned. Is it possible to make a bridge with LTE modem and ethernet ports on MT, so basically MT job would be only powering LTE modem and actlink like switch for it? And all the computers in network behind MT would get DHCP directly from LTE modem etc.

over one year we (the MikroTik customers) wish to add the LTE interface to a bridge to have the public-ip on the ETHERNET port. why is mikrotik ignoring us? wake up mikrotik! we buy your products because we have to build great projects. if you do not add our wishes to your products we will look for other companies and your sales will break in. Thank you!

The problem is not in the MikroTik router, it is in the LTE stick.
The NAT is happening there, nothing MikroTik can do about it!
You should ask Huawei why they are doing this and why the NAT cannot be disabled, as was
usual in sticks from Option.

I can second that it is the USB stick doing the NAT. Even the ones that don't have wifi built in are doing NAT with no supported way to turn it off. The solution I used was to use a mini pci-e card with the routerboard RB912UAG-2HPnD. You need to make sure the LTE card you are using doesn't do NAT, some do but my understanding is most don't. That eliminated NAT for the modem but there is still service provider NAT. You need to talk to your service provider to eliminate that.

If you don't want to do NAT on the mikrotik I believe it is not possible to bridge the LTE card and ethernet port. Reason being bridging is an ethernet layer 2 technology and the LTE card uses PPP which is something else. You can always do 1:1 NAT or probably do plain old routing.