
Operation Manual – Multicast Protocol
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 Multicast Overview
1-9
assigned by IANA; when set to 1, the T flag indicates a transient, or dynamically
assigned multicast address.
z
Scope: 4 bits, indicating the scope of the IPv6 internetwork for which the multicast
traffic is intended. Possible values of this field are given in
z
Reserved: 80 bits, all set to 0 currently.
z
Group ID: 112 bits, identifying the multicast group. For details about this field, refer
to RFC 3306.
Table 1-4
Values of the Scope field
Value
Meaning
0, 3, F
Reserved
1 Node-local
scope
2 Link-local
scope
4 Admin-local
scope
5
Site-local scope
6, 7, 9 through D
Unassigned
8 Organization-local
scope
E Global
scope
III. Ethernet multicast MAC addresses
When a unicast IP packet is transmitted over Ethernet, the destination MAC address is
the MAC address of the receiver. When a multicast packet is transmitted over Ethernet,
however, the destination address is a multicast MAC address because the packet is
directed to a group formed by a number of receivers, rather than to one specific
receiver.
1)
IPv4 multicast MAC addresses
As defined by IANA, the high-order 24 bits of an IPv4 multicast MAC address are
0x01005e, bit 25 is 0x0, and the low-order 23 bits are the low-order 23 bits of a
multicast IPv4 address. The IPv4-to-MAC mapping relation is shown in