Sometimes systemd-networkd-wait-online gets stuck without reason:

# systemctl --failed
  UNIT                                 LOAD   ACTIVE SUB    DESCRIPTION
* clamav-freshclam-once.service        loaded failed failed Update ClamAV virus database once
* systemd-networkd-wait-online.service loaded failed failed Wait for Network to be Online

Legend: LOAD   → Reflects whether the unit definition was properly loaded.
        ACTIVE → The high-level unit activation state, i.e. generalization of SUB.
        SUB    → The low-level unit activation state, values depend on unit type.

2 loaded units listed.

# journalctl -b -u systemd-networkd-wait-online.service | cat
Jun 26 05:10:03 ppcl003.ac.aixigo.de systemd[1]: Starting systemd-networkd-wait-online.service - Wait for Network to be Online...
Jun 26 05:12:05 ppcl003.ac.aixigo.de systemd-networkd-wait-online[1822]: Timeout occurred while waiting for network connectivity.
Jun 26 05:12:05 ppcl003.ac.aixigo.de systemd[1]: systemd-networkd-wait-online.service: Main process exited, code=exited, status=1/FAILURE
Jun 26 05:12:05 ppcl003.ac.aixigo.de systemd[1]: systemd-networkd-wait-online.service: Failed with result 'exit-code'.
Jun 26 05:12:05 ppcl003.ac.aixigo.de systemd[1]: Failed to start systemd-networkd-wait-online.service - Wait for Network to be Online.

# dpkg -l systemd | cat
+-- Desired=Unknown/Install/Remove/Purge/Hold
|+- Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
||+ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||| Name           Version      Architecture Description
+++-==============-============-============-=================================
ii  systemd        261-1        amd64        system and service manager


After login betworking seems to be fine, so WTH is it waiting for? journalctl
doesn't tell.