And here is a journal log of the problem happening. Aug 15 07:36:43 badwlrz-tljss1 ifup[575]: RTNETLINK answers: File exists Aug 15 07:36:43 badwlrz-tljss1 ifup[575]: ifup: failed to bring up eth0 Aug 15 07:36:43 badwlrz-tljss1 systemd[1]: networking.service: Main process exited, code=exited, status=1/FAILURE Aug 15 07:36:43 badwlrz-tljss1 systemd[1]: Failed to start Raise network interfaces. Aug 15 07:36:43 badwlrz-tljss1 systemd[1]: networking.service: Unit entered failed state. Aug 15 07:36:43 badwlrz-tljss1 systemd[1]: networking.service: Failed with result 'exit-code'.
The "File exists" comes from the already existing default route. It is happening very seldomly and looks like a race condition. I don't think any amount of working around this issue by flushing or checking the RA routes is going to help. "ip -6 route replace" should work though.
