RAC: Testing unplanned outage (1 instance goes down)

When you do instance shutdown in sqlplus using shutdown (even abort) or alter pluggable database ... close, srvctl stop database or instance,
Oracle gets that it's you stopping it and it treats it as planned outage. Killing pmon (without -9) works (likely as OS shutdown/restart). On the other hand, for application FCF tests, I am wondering what would be the lighest/fastest way to convince Oracle that unplanned outage just happened (and switch back to retry the test again).

I have crossed somewhere that playing with OS network interfaces can do it, didn't test it yet.
Any other candidate ?

Thank you and regards,
Igor

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