You can have two simultaneous connections, but only one can be DHCP.
For example, you can connect to a WiFi-Direct printer while still having Internet access through your wired network.
XenialDog 64bit (Ubuntu 'Xenial Xerus' LTS, 64-bit)
I think the issue for me a while back was that connection via ethernet cable plugged in the router couldn't go together with wifi (not possible to have both connected) , then you added the "Down" option (Ethernet tab) as workaround.
Also I think you said back then that dhcpcd is able to do that but not udhcpc (I wish could find the thread we discussed about it)
Fred
Also I think you said back then that dhcpcd is able to do that but not udhcpc (I wish could find the thread we discussed about it)
Fred
I misspoke above. Both wlan0 and eth0 above can get their IP addresses by DHCP. But only one can be gateway-ed to the Internet. Otherwise, resolv.conf and the routing table get confused.
In your situation, the dhcpcd daemon automatically takes down an interface when you disconnect it, while udhcpc does not.
In your situation, the dhcpcd daemon automatically takes down an interface when you disconnect it, while udhcpc does not.