The first 4 bits of the IP multicast address are fixed at 1110, corresponding to the high 28 bits of the multicast MAC address. Among the last 28 bits of the IP multicast address, only the last 23…

The first 4 bits of the IP multicast address are fixed at 1110, corresponding to the high 28 bits of the multicast MAC address. Among the last 28 bits of the IP multicast address, only the last 23 bits of the MAC address, so 5 bits of address information are lost. The direct result is that 32 IP multicast addresses are mapped to the same MAC address.