ifconfig down does not work on wifi

The usual way to bring network interfaces up and down was ifconfig <interface> up/down.

This has however been replaced with the mysterious ip command. But ifconfig can still be installed with apt install net-tools.

It does however not work with wireless interfaces when the graphically controlled Network Manager is involved.

Then ifconfig wlan0 down seems to bring it down, because ifconfig -a is no longer listing the interface. This however, is a lie. The interface is still connected, there is no problem to ping or ssh to an IP address connected to it.

To bring it down for real you need to use nmcli, network manager command line interface.

List network connections:
nmcli con 

Connect:
nmcli con up "<name of  connection>"

Disconnect:
Connect:
nmcli con down "<name of  connection>"

Note the very weird "con" which means connection. You can actually only write c or spell out connection if you like to. But it seems popular to type only three letters for some reason.