At boot, networking.service is incredibly slow (5 minutes) on Ubuntu 16.10

Edit /etc/network/interfaces and change "auto" for interfaces to "allow-hotplug"

sudo nano /etc/network/interfaces

Example: auto interface for ethernet card auto eth0 change to allow-hotplug eth0

After that for me "systemd-analyze blame" -> networking.service changes from 5 min to 41 s

I came up with a solution, though it may be more appropriate to call it a workaround.

The problem is that the networking.service has a default timeout of 5 minutes, and for whatever reason, the full timeout period must expire before the boot continues. So, boot takes a little more than 5 minutes.

The solution I came up with is to do the following:

 sudo systemctl edit networking.service

Add the following line:

TimeoutStartSec=10sec

I still have no idea on root cause, and what exactly it is that's timing out, but reducing the timeout from 5 minues to 10 seconds makes the boot up run quite fast, for obvious reasons.

Here's a link to my solution on Ubuntu Forums: https://ubuntuforums.org/showthread.php?t=2342450&p=13569192#post13569192

Hope that helps.