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linuxmulticasttcpdump

linux automatically receive all multicast traffic

Normally you have to do an IP_ADD_MEMBERSHIP for each multicast address you are interested in. If you don't do that then the kernel will drop the packets and you won't see traffic even with tcpdump.

Is there a way to subscribe to all multicast addresses, so you can do a full tcpdump showing all the traffic?

Solution

  • Short answer: no.

    You need to read up on IGMP to understand why.