Hi I have a Huawei E8372 USB stick connected to a RB951Ui-2HD.
The E8371 has issued the IP address 192.168.1.100 to the MT router while it’s own IP address is 192.168.1.1.(I will refer to this as the interLLAN)
On the LAN side of the MT I am using the subnet 192.168.30.0/24. (I will refer to this from now on as the LAN)
When connecting the USB stick to the MT router, the LTE device comes up immediately and I am able to browse the internet from a computer on the 192.168.30.0/24 LAN.
I also have a Grandstream PBX on the same LAN. The trunk on the Grandstream PBX registers with the SIP server on the internet without any problems. I am able to make calls from phones on the LAN to external numbers without any problems with one way audio.
My problem is that I am unable to receive calls. If I look at the connections on the MT router I can see the 5060 conection between the PBX and the SIP server. If I look at the details og this connection, it shows the "Reply Dst. Address as 192.168.1.100. I am assuming that this is the problem. The SIP server is unable to route traffic back to the PBX.
I have tried with ALG turned on and off on the E8372. When ALG is turned on the PBX cannot register with the SIP server, it will only register with SIP ALG turned off. When I tried turning on the SIP helper on the MT, it seems to make no difference whether it is turned off or on.
My question is. Has anyone had experience with this before who will provide an answer for me on this forum? Otherwise is there another device that I can use with a SIM card and 4G that will bypass these problems?