Registering Group Members - Fujitsu XG1200 User Manual

XG1200 User's Guide

4.8.1 Registering Group Members

Upon reception of an IGMP Report message, the XG1200 registers a multicast MAC address with the MAC address table for
the port that received the IGMP Report message and the port to which a multicast router is connected.
The following figure shows the relationship between the registered IP multicast address and the multicast MAC address.
MAC addresses that are registered with IGMP snooping are between 0100.5E00.0000 and 0100.5E7F.FFFF. An IP multicast
address is 32 bits, of which the first 4 bits are always 1110, which are followed by 28 bits to represent its own address
information. Of these 28 bits, the lower order 23 bits are mapped to a MAC address and the data in the higher order 5 bits is
not used. Therefore 32 IP multicast addresses are mapped to the same single MAC address.
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