The raspberry pi 3B is running in Headless Mode. The Ethernet interface seems
only working for the first time the OS is booted, but not since a reboot is
initiated.

(Boot the pi for the first time and shut down, then there is no chance for the
Ethernet interface to come back alive again)

After the power on, the pi seems to be finished its normal booting procedure
but both indicator light of the Ethernet port fails to turn on. The Pi is also
not connected to the router either. There is no chance to start an SSH session,
pinging the Pi's ip address also failed.