Ethernet Multicast Mac Addresses; Ip Multicast Protocols - Huawei Quidway S3500 Series Operation Manual

Operation Manual - Multicast
Quidway S3500 Series Ethernet Switches
224.0.0.12
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1.2.2 Ethernet Multicast MAC Addresses

When unicast IP packets are transmitted on the Ethernet, the destination MAC address
is the MAC address of the receiver. However, when multicast packets are transmitted,
the destination is no longer a specific receiver but a group with unspecific members.
Therefore, the multicast MAC address should be used. Multicast MAC addresses are
correspondent to multicast IP addresses. IANA (Internet Assigned Number Authority)
stipulates that higher 24 bits of the multicast MAC address are 0x01005e and the lower
23 bits of the MAC address is the lower 23 bits of the multicast IP address.
48 bits MAC address
XXXX
X X X X
Figure 1-2 Mapping between the multicast IP address and the Ethernet MAC address
Because only 23 bits of the last 28 bits in the IP multicast address are mapped into the
MAC address, 32 IP multicast addresses are mapped into the same MAC address.

1.3 IP Multicast Protocols

Multicast involves the multicast group management protocol and multicast routing
protocol. At present, the multicast group management protocol uses the IGMP that is
used as IP multicast basic signaling protocol. It is run between hosts and routers,
enabling routers to know whether there are members of the multicast group on the
network segment. The multicast routing protocol is run between multicast routers,
creating and maintaining multicast routes and implementing correct and high-efficient
multicast packet forwarding. At present, multicast routing protocols mainly include
Class D address
32 bits IP address
111 0
XX XX
5 bits not mapped
XXXX XXXX
X X X X XXX X
Huawei Technologies Proprietary
Chapter 1 IP Multicast Overview
DHCP server/Relay agent
All PIM routers
RSVP encapsulation
All CBT routers
Designated SBM
All SBMS
VRRP
......
XXXX XXXX
XXX X XXXX
Lower 23 bits directly mapped
XXXX XXXX
XXXX XX XX
1-4
Meaning
XXXX
X X X X
XXXX
X X X X