4g modem that can connect to upstream wifi and provide 4g backup if wifi drops out

[BlizzardX]

Hi folks

I've got a security system with a base unit that is connected via the internet and requires the internet to operate. Currently if we suffer a power or internet cut, the security system is rendered useless as it can't operate as my internal network either drops out or there is a lack of internet.

I'm looking for a device, possibly 4g modem(?), that can bridge the device and the network and allow the device to failover to 4g if the wifi or main internet drops out. The base unit of the security system has ethernet to avoid wifi problems and has battery backup.

I think I can use an old 4g mobile phone with a usb-c ethernet adapter and apps that monitor the internet connection via wifi and then swtich across the connection to 4g on loss but thats kinda ugly and I'm looking for some form of neater unit.

Simple Diagram:

Cameras / panels / sensors > Security System Wifi > Homebase > 4g device offering failover > Internal Wifi or 4g Internet

Any recommendations?

 

[BigT]

I think what you need here is a UPS, a router capable of WAN failover and a 4G device plugged into that new router as well as your existing internet connection.

Just be careful with 4G and security systems because 4G (unless you pay for a special SIM) uses CGNAT which means while under 4G you can’t reach things via external IP or dynamic DNS etc. As a rule of thumb if your security system requires you to subscribe to a cloud service you should be OK but if you VPN in it’ll not work on regular 4G as you won’t be able to instigate a connection to your VPN server.

So in your diagram you’d replace the right hand side with:

homebase > dual WAN router ( > existing internet AND > 4G modem/router )

You‘d make sure the router and everything to the right is powered via UPS. The dual WAN router’s software can be configured to monitor and flip between internet connections depending on their state.

As for recommendations I use a mini ITX PC running pfSense as the dual WAN router and a TP-Link 4G router into that. Easier dual WAN router solutions using a 4G USB dongle that I know of are available from Draytek and Ubiquiti. A whole host of consumer and enterprise stuff too.