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.