…when the ethernet cable is disconnected during boot or, in my case, the Raspberry Pi is connected via USB to the router and powered up simultaneously, even if the ethernet cable is cycled.
Steps to reproduce:
- Disconnect ethernet cable
- Power on Raspberry Pi
- Wait for boot to be completed
- Insert ethernet cable
eth0 should go up and an IP address should be fetched via dhcp
# systemctl restart networking
- or in my case -
ExecStartPost=systemctl restart networking
under [Service] to /lib/systemd/system/mpd.service as the router is ready by then.