This bug was fixed in the package systemd - 229-4ubuntu21
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systemd (229-4ubuntu21) xenial; urgency=medium
* networkd: do not uncoditionally apply NOARP.
* networkd: fix size of MTUBytes so that it does not overwrites ARP.
* Fixes regression-updates LP: #1727301
-- Dimitri J
** Changed in: systemd (Ubuntu Zesty)
Status: Confirmed => Invalid
** Changed in: systemd (Ubuntu Bionic)
Status: Confirmed => Invalid
** Changed in: systemd (Ubuntu Artful)
Status: Confirmed => Invalid
--
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** Changed in: systemd (Ubuntu Zesty)
Status: Fix Released => Confirmed
** Changed in: systemd (Ubuntu Bionic)
Status: Fix Released => Confirmed
** Changed in: systemd (Ubuntu Zesty)
Importance: Undecided => Critical
** Changed in: systemd (Ubuntu Artful)
Status: Fix Rele
** Description changed:
+ [Impact]
+
+ * Incomplete cherrypick of ARP functionality in networkd resulted in an
+ undesired side-effect, specifically NOARP flag started to be applied
+ unconditionally, specifically when it should not have, resulting in loss
+ of network connectivity.
+
+ * This
I am suspecting the following cherrypick is missing in xenial:
https://github.com/systemd/systemd/commit/1ed1f50f8277df07918e13cba3331a114eaa6fe3.patch
will prepare a PPA with this fix applied, and will expedite an sru with
this fix in.
** Bug watch added: github.com/systemd/systemd/issues #389
