10G Core Routing Switch User Manual
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As Internet Assigned Number Authority (IANA) provisions, the high 24 bits of a multicast MAC address are 0x01005e
and the low 23 bits of a MAC address are the low 23 bits of a multicast IP address.
Figure
Mapping between a multicast IP address and an Ethernet MAC address
The first four bits of the multicast address are 1110, representing the multicast identifier. Among the rest 28 bits, only
23 bits are mapped to the MAC address, and the other five bits are lost. This may results in that 32 IP addresses are
mapped to the same MAC address.
IP Multicast Protocols
Multicast involves multicast group management protocols and multicast routing protocols. Their application positions
are shown in follow Figure Application positions of multicast-related protocols.
Figure
Application positions of multicast-related protocols
I. Multicast group management protocol
Multicast groups use Internet group management protocol (IGMP) as the management protocols. IGMP runs between
the switch and multicast router and defines the membership establishment and maintenance mechanism between
them.
II. Multicast routing protocols