Ethernet and wifi interfaces active at same time?

Hi I am referencing below from this closed thread: 

So currently I set up wifi through an initial ethernet connection, but the issue is when the wifi connection is successfully setup,  that connection does not become active until ethernet is unplugged and board rebooted. Wifi is setup through nmcli...is there an option we are missing that is preventing both network interfaces from working simultaneously?

currently just using "sudo nmcli dev wifi connect ssid password password"

Quote

 

That's simply not true. In case you already established a Wi-Fi connection to your AP (using nmtui or nmcli) then simply do the following:

shut your SBC down

unplug Ethernet cable from your SBC (this is totally unrelated to OPi Zero, I emphasize on this since a few morons on the net constantly claim OPi Zero would have non working Wi-Fi)

restart your AP

power your SBC on

Try SSH over Wi-Fi now and you're in. The whole 'problem' boils down to legacy sun8i kernel behaviour, MAC addresses, ARP tables/caches, routing settings on your AP when you first connect your SBC with both Ethernet and WiFi to the same network (your AP/router is involved here too). As soon as your AP doesn't remember to connect to your WiFi MAC address through the Ethernet interface the problem is solved. So what you're running into is only caused by (temporarely) connecting your SBC with both network interfaces to the same AP/router that is most probably configured as a bridge between wired/wireless using same IP address range.