Fix for error "Network Device not managed" in ubuntu

I was configuring DHCP Server, after configuration successful i restarted my server then All Ethernet ports went down, i check Network Manager graphically it shows "Device not managed" then i checked it from terminal using

sudo /etc/init.d/networking restart

It gives me this message

* Running /etc/init.d/networking restart is deprecated because it may not enable again some interfaces
* Reconfiguring network interfaces...                                        
/bin/sh: cannot open /etc/iptables_rules: No such file
Failed to bring up eth0.

This was the issue i got.
Now Solution!!!

Edit the file "/etc/NetworkManager/NetworkManager.conf"
 Change managed=false to managed=true

And ececute this in terminal.

sudo killall NetworkManger

Now we can configure our ethernet/wify interface.