Comment 52 for bug 1301015

I can't believe this very important functionality has been removed and there is no alternative solution given for reading the /etc/network/interfaces file (except reboot)

Ifconfig solution doesn't read the configuration files. It is unacceptable.

There must be a script that reads this file. Where is it? How to trigger it?
Is it the same with debian?

This feature is documented everywhere:
http://ubuntuguide.org/wiki/Ubuntu_Trusty_Networking

As long as no viable alternative solution is given, this has to be considered a very important bug.