H3C S5500-EI Series Operation Manual page 15

Operation Manual – Multicast
H3C S5500-EI Series Ethernet Switches
Figure 1-4 IPv6 multicast format
0xFF: 8 bits, indicating that this address is an IPv6 multicast address.
Flags: 4 bits, of which the high-order flag is reserved and set to 0; the definition
and usage of the second bit can be found in RFC 3956; and definition and usage
of the third bit can be found in RFC 3306; the low-order bit is the Transient (T) flag.
When set to 0, the T flag indicates a permanently-assigned multicast address
assigned by IANA; when set to 1, the T flag indicates a transient, or dynamically
assigned multicast address.
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
Reserved: 80 bits, all set to 0 currently.
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
0, 3, F
1
2
4
5
6, 7, 9 through D
8
E
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.
Value
1-9
Chapter 1 Multicast Overview
Table
Meaning
Reserved
Node-local scope
Link-local scope
Admin-local scope
Site-local scope
Unassigned
Organization-local scope
Global scope
1-4.