❯ uname -a
Linux $HOST 5.12.17-2-MANJARO-ARM #1 SMP PREEMPT Fri Jul 16 18:21:07 CDT 2021 aarch64 GNU/Linux
Display/Keyboard: I don’t have a monitor or keyboard plugged into this thing. It’s meant to be an SSH-only server.
Topography: Pi 4b is connected to network via internal 1Gbps Ethernet port. Same behavior with direct connection to router or direct connectoni to switch.
Testing: After I noticed that none of the computers on my network that use Pi-Hole for their DNS could actually resolve anything, I tried:
- Accessing the web interface, and couldn’t get that to load.
- Logging into the server via SSH. Host unavailable.
- Ping. Host unreachable.
- Hard rebooting the Pi (with the power button on my Canakit PSU).
- First reboot: no effect (still can’t ping);
- Second reboot: pingable for a minute or so, then host not found.
- Moving the Pi from a 1Gbps port on my router to a 1Gbps port on a switch connected to the router.
Nothing worked. Moving it to the switch was helpful, as the switch UI actually displays a very easy to use live graph for connected devices’ network usage. I was able to verify that there is NO network activity at all from the Pi when I can’t connect to it.
Solution (at least, to the problem of network connectivity):
Letting the Pi boot up, and then unplugging and replugging the ethernet cable while the device is powered on. This restores
Well… this is new. I’m not sure when this started–I know it wasn’t after the latest stable update, as I rebooted without issue, then.
Not really sure how to troubleshoot this. On one reboot, I got a unit failure notice on
systemd-networkd-wait-online.service, but that didn’t happen on the next reboot, even though I still had to unplug and replug the cable.
Any ideas? Or any particular diagnostic info that would be helpful?
EDIT: I’ve confirmed that traffic itself doesn’t appear to contribute to the instability. I let a continuous ping cycle run overnight from one of my other computers to the Pi, and it maintained connection with zero percent packet loss.
Pretty sure that one lost packet is from me terminating the
44460 packets transmitted, 44459 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.115/0.289/3.145/0.114 ms