How to correctly configure SIP (Mango Office) + MikroTik + 4G LTE USB (MTS)?

Question

SIP

Hello!
Now it's my turn to ask the community for help.
The situation is the following. There is an IP telephony provider - Mango Office. There were never any questions to him, everything worked like clockwork, equipment (a couple of IP phones have been set up for a long time). Both phones are connected to Mikrotik. Network access was via a USB whistle, but the PPPoE connection was raised by the Mikrotik itself. In this case, everything was OK, everything worked (both telephony and Internet access for employees).
Now the situation has changed a little - a new modem has been inserted (ZTE 830FT it seems), which the connection raises itself. Further — the Internet is, everything works, but the telephony lies tightly. The nearest available Cisco SPA303 phone says: “Failed, Not Registered, No Response” ... The second IP phone (some kind of Panasonic) is also not ale. The IP address on which the phones from the workstation are registered is pinged.
The question is - what has changed such that everything has collapsed? How to set everything back in the new realities? I apologize for the chaotic presentation of the question, but this is already beyond good and evil :(

Answer 1

The way NAT works has changed, now that modem is doing it, and not the microitk, respectively, either the SIP support mechanism built into the MK (IP - FireWall - Service port) used to work, but now it doesn’t, or the modem cuts any connection. You need to twist the NAT settings in the phones and / or the NAT settings in the whistle.

Answer 2

As far as I remember - ZTE 830FT does not know how to SIP ALG. Look for Huawei modems like e3372s\e3372h etc. they can be altered as you like and they work fine with SIP.

Answer 3

Well, read here :)
www.mikrotik.by/index.php?s=9a1418512fd3428e32f56e...

Answer 4

@totalcount the problem is most likely that the connection raises the modem, not the microtic, i.e. you want to distribute the Internet from the modem to the microtic via USB?

Answer 5

By default, MikroTik already has a setting that helps SIP work from under NAT (and this is normal in the modern realities of the lack of IPv4), and you don’t need to forward any ports, since MikroTik looks at the SIP protocol by default and replaces the IP set there with its external one. Thus, from the outside it looks like there is no NAT. If you need to disable/enable this option, you can find it here:
ip-->firewall-->service-port-->sip, enable (blue tick)/disable (red cross).
And since you have shifted this responsible function to 4G LTE USB (MTS), therefore NAT needs to be organized on it or look for another hardware or solution.