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[Iam_TJ]

I was looking at the Zyxel 3G/4G USB cellular modem compatibility list but unfortunately they don't note which are 4G.

Has anyone experience of sucessfully using a 4G USB cellular modem with the VMG8924, and if so, what make and model?

I've got a Huawei E3131 3G in CDC-Ethernet mode (presents as an Ethernet port and has to be enabled via a web interface) which appears to be supported by the v18 firmware - as in, doesn't need to pull any tricks with usb_modeswitch to put it into 'traditional' serial port emulation mode.

When the cellular modem is attached the VMG8924 figures out it's web-interface address and adds it's link sub-net (192.168.1.1/32) to the routing table. The modem has to be configured to Auto-Connect otherwise it can't be automatically enabled by the VMG8924 so auto-failover wouldn't be possible, because the user would have to visit the E3131's web server and press the "Connect" button to bring up the 4G link itself. A link to that interface is presented on the VMG8924's Network Setting > Broadband > 3G Backup page.

The other issue I can foresee for some users is that if their local sub-net is 192.168.1.0/24 then the router will get very confused about routing, doubly so if they've a device on the internal side also using 192.168.1.1. I'd have used some iptables magic to put it on an out-of-the-way IP address in the class A 10.0.0.0/8 range.

[Iam_TJ]

I opened a support request with Zyxel. The initial response was that no 4G cellular modems are supported.

I pointed out that the problem is with the out-of-date and inaccurate web-page an '3G' publications. The routers do support 4G cellular modems (they can't care less in most cases what's on the cellular side).

What's important is what is presented by the cellular modem on the client-side to the router.

In the case of most Huawei devices which use the "HiLink" software internally (an embedded HTTP server and set of configuration/status pages) these will work without problems provided that the usb_modesewitch open-source software embedded in the router firmware 'knows' how to switch the device from it's initial fake CD-ROM mode (for Windows users to install the drivers) to it's data mode. This may infer that very new devices might not be known to usb_modeswitch and therefore might not be supported until later firmware releases.

I've found that the Huawei E3372 (4G 150Mbps) works fine in exactly the same way as the E3131 (3G HSPA+).

I've spotted one bug though - the router's Network Map status GUI shows the active connection as "3G" when the cellular modem is connected but not active. The default route remains on the PPP xDSL connection. This might cause some owners to have heart palpitations at the thought of the data charges the modem might be racking up!