One of the most powerful but less well-known options of OpenVPN is the management interface. The management interface is available on both the server side and the client side. On the server side, it can be used to collect statistics, monitor and control the connected clients, and perform other management related tasks. On the client side, it can be used to query for passwords, enter proxy information for establishing a connection with the VPN server, interact with a PKCS #11 device, and collect client-side statistics.
The OpenVPN plugin for the Linux NetworkManager makes extensive use of the management interface to control the startup and shutdown of the VPN connection.
To use the management interface, add a line
management 127.0.0.1 23000 stdin to either the client or the server configuration file. This option instructs OpenVPN to set up the management interface on IP address 127.0.0.1, port 23000, and to use
stdin to specify the management password.