On a clean Kubuntu 18.04 install (plasma 5.12.5, framework 5.44.0, Qt 5.9.5) I applied the following sequence: open "System Settings/Network/Connections" select current connection in tab "IPv4" set "Method:" to "Automatic (Only addresses)" set "DNS Servers:" to "1.1.1.1, 1.0.0.1" in tab "IPv6" set "Method:" to "Automatic (Only addresses)" set "DNS Servers:" to "2606:4700:4700::1111,2606:4700:4700::1001" click "Apply" open "Terminal" execute "sudo service network-manager restart" > After this I kept seeing "setting network address" followed by "disconnected" in a repeating loop. > I reset the DNS values to the system defaults, restarted the network-manager, rebooted; the problem persisted. > I reinstalled Kubuntu 18.04, setup a VM of Kubuntu and applied the same custom dns sequence in the VM and it worked. > So I tried the sequence on my reinstalled system and it worked, until I rebooted.
I've now tested this on 3 other systems, and the sequence works without a flaw. I guess the problems I have on my system setting up DNS is somehow hardware related.
I now know it's not just a problem when changing DNS, it also happens when I set a cloned MAC address. I suspect changing anything in the "Connections" causes the network to fail, and changing settings back & rebooting does not make it work again. In fedora 28 with plasma (5.12.5) it's also happening. In KDE Neon 16.04.4 useredition (5.12.5) there's no problem. I've come across another system (also with a pre 2012 motherboard) that has the same problem with Kubuntu 18.04. So it's not an isolated case.
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This bug has been in NEEDSINFO status with no change for at least 30 days. The bug is now closed as RESOLVED > WORKSFORME due to lack of needed information. For more information about our bug triaging procedures please read the wiki located here: https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging Thank you for helping us make KDE software even better for everyone!