Hi,
I've just bought a Huawei E3372h-607 USB LTE Modem which appears to have the HiLink "router-on-stick" style firmware.( am using a GL.iNet MT300n-V2 "Mango" router flashed with openwrt-19.07.5.
It works fine - it appears it only needs opkg update && opkg install kmod-usb-net-cdc-ether usb-modeswitch, and then after a reboot the modem presents itself on eth1 - I just went to interfaces > new > eth1 > type: dhcp client, assigned it to "wan" firewall zone and voila - everything works. I get a 192.168.8.xxx address on this interface, and I can access the modem's webUI via a browser connected to my OpenWRT's LAN by aiming a browser at 192.168.8.1 I am getting 30 megabits/sec up and about 25 megabits/sec. I am happy with this performance - this is my road warrior setup so I don't care about top speed, reliability is key.
I know this setup means you're double NATing - once from my 192.168.1.0/24 network -> 192.168.8.0/24 HiLink network then again from the HiLink network through to the WAN IP that my cellular provider is handing out. Triple NAT if you count the CGNAT they're doing.
But really, does it matter? I mean the speed is adequate, the connection in stable. Is there any benefit in changing this from a HiLink ethernet device through to a PPP device so that I can enter my APN etc directly on OpenWRT and have OpenWRT responsible for establishing & maintaining the PPP session?
I'm just wanting to make sure I'm not missing anything. I'm inclined to leave it as it is as it "works".