Switches will send packets to all interfaces when using broadcasts or under extreme conditions (full MAC Address Table). This can lead to duplication if there is a loop between two or more switches and if the Spanning Tree Protocol is not used. So the answer is rarely.
That is extraordinarily rare and I’m not even sure if it’s possible anymore. That was potential attack vector in the 90’s where you have a port on network switch, and then you flood the cam table with thousands of bogus mac addresses until you fill it up, then the switch turns into a hub, and you can now sniff all traffic traversing the switch. These days I’m not sure what will happen if you do successfully fill up a switches cam table. Also cam table sizes are are much much larger now. ~128k entry’s vs maybe 1000 back in the day.
From StackOverflow:
https://stackoverflow.com/questions/9196791/duplicate-udp-packets-how-often-it-happens#9220574
That is extraordinarily rare and I’m not even sure if it’s possible anymore. That was potential attack vector in the 90’s where you have a port on network switch, and then you flood the cam table with thousands of bogus mac addresses until you fill it up, then the switch turns into a hub, and you can now sniff all traffic traversing the switch. These days I’m not sure what will happen if you do successfully fill up a switches cam table. Also cam table sizes are are much much larger now. ~128k entry’s vs maybe 1000 back in the day.