I am not sure if my answers are reaching the users because i did not received it back so sorry to creating a new thread, but i think this is very important, please follow this steps to emulate it:
1- Install Debian 9.6 without graphical interface. 2- Try to change the ip in /etc/network/interfaces 3- Run systemctl restart networking ping 8.8.8.8 (network stopped working!) If system is restarted everything is ok again, and ip is changed properly . New try, now with ifdown and ifup: 1- Install Debian 9.6 without graphical interface. 2- Try to change the ip in /etc/network/interfaces 3- Run ifdown enp0s3 4- Run ifup enp0s3 5- That's right ,but now you have two ips configured instead of changing it. Is this is expected, i am so sorry for boring you, i will get out of here the faster as i can. -- Luciano Andress Martini - Analista UNIX