$ sudo SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-networkd
timestamp of '/etc/systemd/network' changed
sd-rtnl: discarding 20 bytes of incoming message
eth0            : link 2 added
eth0            : udev initialized link
eth0            : flags change: +UP +LOWER_UP +RUNNING +MULTICAST +BROADCAST
eth0            : gained carrier
lo              : link 1 added
lo              : udev initialized link
lo              : flags change: +LOOPBACK +UP +LOWER_UP +RUNNING
lo              : gained carrier
eth0            : link state is up-to-date
eth0            : found matching network '/etc/systemd/network/80-dhcp.network'
eth0            : acquiring DHCPv4 lease
DHCP CLIENT (0x6551415c): STARTED on ifindex 2 with address f2:3c:91:73:5a:2f
eth0            : discovering IPv6 routers
ICMPv6 CLIENT: Start Router Solicitation
eth0            : enslaved
eth0            : link configured
Sent message type=method_call sender=n/a destination=org.freedesktop.DBus object=/org/freedesktop/DBus interface=org.freedesktop.DBus member=Hello cookie=1 reply_cookie=0 error=n/a
DHCP CLIENT (0x6551415c): DISCOVER
ICMPv6 CLIENT: Sent Router Solicitation
lo              : getting address failed: Device or resource busy
Got message type=method_return sender=org.freedesktop.DBus destination=:1.16 object=n/a interface=n/a member=n/a cookie=1 reply_cookie=1 error=n/a
lo              : link state is up-to-date
lo              : unmanaged
Got message type=signal sender=org.freedesktop.DBus destination=:1.16 object=/org/freedesktop/DBus interface=org.freedesktop.DBus member=NameAcquired cookie=2 reply_cookie=0 error=n/a
sd-rtnl: discarding 20 bytes of incoming message
eth0            : added address: fe80::f03c:91ff:fe73:5a2f/64
eth0            : added address: 2a01:7e00::f03c:91ff:fe73:5a2f/64
lo              : added address: ::1/128
lo              : added address: 127.0.0.1/8
ICMPv6 CLIENT: Received Router Advertisment flags none/none
DHCP CLIENT (0x6551415c): DISCOVER
DHCP CLIENT (0x6551415c): DISCOVER
DHCP CLIENT (0x6551415c): DISCOVER
DHCP CLIENT (0x6551415c): DISCOVER
^[[AICMPv6 CLIENT: Received Router Advertisment flags none/none