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Would like to have some clarification on following scenario:

  1. There is Linux platform with an Ethernet interface which has some constant default IP address (eth0: 10.0.0.1) and some changing IP address (eth0:1 20.20.20.20). Meaning, both have same MAC address.
  2. There is an IGMP V2 join message sent out from 20.20.20.20 to multicast group 225.1.1.1
  3. There is an IGMP V3 leave message sent out from 10.0.0.1 to multicast group 225.1.1.1.

What are the possible effects of this?

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It depends.

If your switching infrastructure is IGMP-aware (IGMP snooping), the IGMP leave group is translated to an Ethernet multicast leave group and that causes the switch port to disable forwarding for that group. However, the next query would rejoin the port to the IGMP group.

Without switch IGMP support, multicasts are flooded like broadcasts, making them work continuously.

Note that 225.0.0.0/8 is reserved by IANA and shouldn't be used (check RFC 5771).

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