How to capture Multicast packets in wireshark

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Exactly the same way like any other ones. But the first thing you have to do is to make sure that they arrive to the network card you use to capture. So if the card is connected to a managed switch which only outputs multicast packets on ports to which a subscription for that multicast group came before, you may not see them even if your capturing card is in promiscuous mode because the switch won't send them to you.