Comment 12 for bug 1664844

On Thu, May 25, 2017 at 04:00:16AM -0000, Mike Pontillo wrote:
> Well, to clarify, I guess I'm not 100% happy with that. ;-)

Nor should you be! As I said, this is a valid bug.

> What you describe will work for the majority of server and cloud use
> cases. But installing Ubuntu on a router (or L3 switch) will be
> problematic if nothing happens when links go up or down. Actions need to
> be taken, such as adding or removing routes, so that the kernel doesn't
> attempt to route traffic to link-down interfaces.

Of course, but that is not a function of the netplan yaml declaration; it's
a function of the network config renderer. ifupdown has *no* policy daemon
for handling link-up/link-down events, therefore with ifupdown you don't get
any sensible handling. networkd and NetworkManager should both handle
link-down events correctly. If you find that networkd is *not* handling a
link-down event by removing the routes, please file a bug on systemd for
this and reference it here so we can prioritize resolving it.

The original bug report here that is relevant to netplan is not about
handling transitions between link-up/link-down state, it's about being able
to provide configuration for a network interface with the intent that either
a) this interface will not be automatically brought up, or b) this interface
will not be considered towards network-online status.

On Thu, May 25, 2017 at 03:54:17AM -0000, Mike Pontillo wrote:
> This bug was observed with a backport of Netplan running on Xenial with
> systemd.

If you specifically observed that sshd was not running on a system that had
at least one up interface, that is not the designed behavior and I don't see
any way that this would be a result of a netplan or networkd bug. Please
report a bug on systemd if this is reproducible.

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