in /etc/network/interfaces: "auto" vs "allow-hotplug"

[Rick Thomas <rbthomas@pobox.com>]

I have two machines (out of a group of ten) that will not bring up their ethernet interface at boot time if the interfaces is of type “allow-hotplug”.  When I change that to “auto” the interface comes up at boot with no problem…

The remaining eight machines have no problem with allow-hotplug. (which is the default as setup by the d-i)

It does not seem to correlate to kernel version.  The two “auto” machines are running 4.12 and 4.9;  The “allow-hotplug” machines are running anything between 3.16 and 4.12.

Nor does it seem to correlate with static vs dhcp.  The two “auto” machines are both using dhcp.  The “allow-hotplug” machines are using a mixture of static and dhcp.

Anybody have a clue as to what’s going on?

Thanks in advance…
Rick