In order for multicast to work, the source and the destination must be linked by multicast-enabled routers. Multicast cannot operate when the target is directly connected to the test station. Moreover, the router(s) between the target and the test station must support the IGMP protocol.
The goal of this test is to validate that the driver properly configures the MAC filter to allow the multicast packets to be passed by the µC/TCP-IP module when the target is registered to a multicast group. Also, the test ensures that, when the target is unregistered from the multicast group, multicast packets are dropped by the MAC filter.
...