H3C Technologies H3C SecPath F1000-E - Manual (Page 9)

8
Bit Description
R
• When set to 0, it indicates that this address is an IPv6 multicast address without an
embedded RP address
• When set to 1, it indicates that this address is an IPv6 multicast address with an embedded
RP address (the P and T bits must also be set to 1)
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: 4 bits, indicating the scope of the IPv6 internetwork for which the multicast traffic is intended.
Possible values of this field are given in
Table 5 .
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: 112 bits, IPv6 multicast group identifier that uniquely identifies an IPv6 multicast group in
the scope defined by the Scope field.
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 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
0, 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 Figure 6 .