Internet disabling function, or Kill Switch, when disconnecting from VPN is implemented in applications for Windows, macOS and iOS. The last two are enabled by default and are called “Connection Protection”.
In the Windows application, you need to open the settings, the "General" tab, switch the Kill Switch option to the options "when connected" or "when the program starts."
A simple option to protect a real IP address from detection in case of accidental disconnection or at the time of switching between servers can be implemented by setting up a second VPN connection on the router. It will turn out to be something like Double VPN. Thus, in the event of a disconnection of one of the VPNs, the second will be active.
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