H3C Technologies H3C S10500 Series Switches - Manual (Page 23)

8
Bit Description
P
• When set to 0, it indicates that this address is an IPv6 multicast
address not based on a unicast prefix
• When set to 1, it indicates that this address is an IPv6 multicast
address based on a unicast prefix (the T bit must also be set to 1)
T
• When set to 0, it indicates that this address is an IPv6 multicast
address permanently-assigned by IANA
• When set to 1, it indicates that this address is a transient, or
dynamically assigned IPv6 multicast address
• Scope—The Scope filed contains four bits, which indicate the scope of the IPv6 internetwork for
which the multicast traffic is intended.
Table 5 Values of the Scope field
Value Meaning
0, F Reserved
1 Interface-local scope
2 Link-local scope
3 Subnet-local scope
4 Admin-local scope
5 Site-local scope
6, 7, 9 through D Unassigned
8 Organization-local scope
E Global scope
• Group ID—The Group ID field contains112 bits. It uniquely identifies an IPv6 multicast group in the
scope that the Scope field defines.
Ethernet multicast MAC addresses
A multicast MAC address identifies a group of receivers at the data link layer.
1. IPv4 multicast MAC addresses
As defined by IANA, the most significant 24 bits of an IPv4 multicast MAC address are 0x01005E. Bit
25 is 0, and the other 23 bits are the least significant 23 bits of a multicast IPv4 address.
Figure 6 IPv4-to-MAC address mapping