This morning due to a power failure my router restarted, but after coming up again, I had no Internet access. We haven't changed anything on the router in a while, so my first thought was an ISP issue. But they said all ok to the on-prem router.
As a trial I started disabling functions in our router to see if I could isolate the problem. When I disabled the Zerotier interface, I regained internet access. So, I did a little more digging, I re-enabled the interface, and the internet still worked.
I then rebooted the router again, from the console this time. And the same thing happened, no internet access until I disabled the zerotier interface. Once, diabled internet returned, then enabling the zerotier again allowed it to work, and I still had internet access.
Has anyone else experienced this? Is there a fix or workaround, other than me having to perform these manual tasks each time the router restarts?
I'm experiencing the exact same behavior, on my Proxmox OPNsense VM. Same solution as you mentioned as well. I have not had a chance to poke around and find out exactly how to resolve this problem. I hope someone has some insights.
Saw that in my tests today. It created a gateway even though I marked " This interface does not require an intermediate system to act as a gateway". After the reboot, that gateway is marked as "active" and I get no Internet traffic to the LAN.
Fix for me was to disable the gateways associated with the ZT interfaces.