Boron w/ Ethernet Featherwing + LTE

Hello all, I recently purchased a Boron LTE and an ethernet featherwing with the intention of using both LTE and Ethernet simultaneously. LTE would be used for cloud/internet access and the wired ethernet would communicate with other local devices. Both LTE and ethernet would be used to process requests like, toggle I/O, read adc, etc… The wired ethernet network would have no internet access.

I came across the following post from Nov’19 where it was determined that this was not possible: Boron w/Featherwing Connectivity

Does anyone have any experience with running ethernet and LTE at the same time? Thanks for your time.

*Edited for clarity

On first check it does appear that using LTE and ethernet simultaneously is a no go. When connected to an ethernet network with no internet access I am unable to access the device vie LTE…

There will be a couple problems with this setup.

One is that the the Ethernet FeatherWing only supports DHCP addressing. It does not support static IP addressing, so it won’t work on an isolated network that doesn’t have DHCP.

The other problem is that as soon as the Ethernet has link and an IP address, Device OS will attempt to use it for the Internet/cloud connection, even if the network is isolated and can’t connect to the Internet. It will never fall back to cellular once the Ethernet interface is up.

With a sufficient amount of effort and modification of Device OS it may be possible to work around these issues, but it’s not a trivial change.