I have a Fedora 28 server in my lab that has multiple network adapters, but only one of them is cabled to a switch. All the software is updated to NetworkManager-1.10.12-1.fc28.
However, when I run journalctl -e I typically see pages and pages and pages of DHCPDISCOVER requests on the non-connected ports, constantly retrying. The logs fill very, very fast.
I did something yesterday that managed to cause the retrying to stop, leaving the unused ports all in the disconnected state (nmcli device status said disconnected for each one). I thought, hmm... well that problem is now fixed. `journalctl -e` showed everything quiet.
Today, I thought I'd check. When I did `journalctl -e` there were no DHCPDISCOVERs issued, and when I did `nmcli device status` the ports were all still "disconnected".
But then I did `nmcli con show`. It said the ports were in a disconnected state.
However at this point I happened to repeat the `journalctl -e` command, and my goodness - the stream of DHCPDISCOVER requests timing out were a sight to amaze, and the network manager kept transitioning the state of the ports that had no cables correspondingly, trying to get an IP address.
This may be my misunderstanding, but the interface knows whether the port is connected to some other port with a cable or if it is not. It seems logical also that merely asking for the connection status shouldn't "turn on" a lot of useless DHCP discovery on disconnected ports.
So am I confused or is this a bug?
Tell me what you need to find it if so.
I'd also like to know how to stop the behavior. I know I could change the ports to not be "auto", but I'd really like to be able to just plug a cable in and start using the port to talk to some other system or switch.