Ethernet and Wifi at the same time

Using a Jetson Nano with the Ubuntu 20 image from QEngineering. I have the Intel 8265AC wifi card installed and was working prior.

I am trying to eventually get the Jetson to connect to a LAN network via the Ethernet and have the WiFi card spawn a hotspot. To connect to the LAN network, i set the static IP by creating a eth0 file within /etc/network/interfaces.d/. On reboot, the Jetson can successfully be found on the LAN network, but the WiFi card is no longer found. When I use the Setting GUI, the WiFi tab presents “no wifi adapter found” but when I use sudo lshw -C network in a terminal it finds the wifi adapter. Also am still able to ssh into the Jetson via WiFi, even though it does not explicitly say I am connected to the network besides the IP address.

This is not we can support, please contact with them. Thanks

I also cannot answer, but I will give a slight background on this…

Some network devices are “managed”, others are not. The setup changes depending on which type. Your ethernet is intended to run regardless of who logs in, but the normal setup is for Wi-Fi to run only with a GUI login, owned by whoever logs in to the GUI.

With two “overlapping” networks (serving access to the same networks, not independent networks) you have a choice of either disabling one (to avoid conflict), or else to change the priority such that one is higher priority than the other, and the kernel chooses the highest priority network (which might change depending on what network you are trying to reach). The choice by default is to disable one depending on if someone is logged in to the GUI or not.

There are cases known as “bonding” whereby two separate networks which are more or less identical can be used simultaneously to double bandwidth (it isn’t really double, but in theory it could reach double). Half the packets might go over one, and half over the other simultaneously. In that case both networks would have exactly the same priority and the kernel would perform some sort of load balancing.

The priority is the “metric”. Run the command “route” and you’ll see it based on each interface and a network mask. A lower metric is a lower “cost”, and so a metric of 0 is higher priority than a metric of 100. Loopback, the internal network which does not require any network devices and which goes only to itself is always the lowest priority and only goes to the local host (which is why it has the alias “localhost”).

What you’re asking for is to not remove one network when the other is up. Those two networks differ quite a bit in performance though, and so they would have to have different metrics/priority, which is generally set up at the time the network is started. If both had the same metric, then it wouldn’t work correctly unless you had bonding set up, and even then, with the difference in performance between the two, bonding would be bad.

More interesting is something like a cellular network whereby you might have three cell towers simultaneously in range. Each tower would know the performance from traffic load and RF conditions, and set a metric relative to that. The metric could change in real time. The packets (cell phones are digital network data) would route to the lowest metric (highest priority) at any instance in time; as the user drives along or moves and tower access changes, the metric, and perhaps even which cell tower is available in the top 3 list, would change. The metric would adapt.

I can’t tell you how to do what you want, but you’ll probably need to either manage these as static networks (which don’t stop and start when other network devices stop and start), or somehow set them up to avoid needing to be logged in (and to be owned by root for the Wi-Fi instead of being controlled by the individual for the Wi-Fi). You’d also need to choose the correct metric, because if Wi-Fi is always there and always the higher priority (lower metric), then there would be no need for the other network device. If Wi-Fi were ever the higher priority, and not available, then networking would fail; the Wi-Fi would need to either change metric or be removed from service for ethernet to work in its place.

The one time when this might be useful to normal usage (that I can think of) is if the Wi-Fi has access to different network subnets than does the wired ethernet. Let’s say you have a secure network with no Wi-Fi access, and that secure network itself is not connected to the outside internet. This would mean that you could have a missing route to a particular subnet (infinite metric, no priority, infinite cost) on one device via the route function, while the other network device has access (a non-trivial, but realistic metric) to that same subnet. You could easily make use of Wi-Fi for general use for that case, and use only wired to reach the secure subnet.

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