HP A6600 Configuration Manual page 19

Table 5 Values of the Scope field
Value
0, F
1
2
3
4
5
6, 7, 9 through D
8
E
Group ID—Contains 112 bits and uniquely identifies an IPv6 multicast group that is within 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, 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.
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 remaining 23 bits are the least-significant 23 bits of a multicast IPv4 address.
Figure 6 IPv4-to-MAC address mapping
The most-significant four bits of a multicast IPv4 address are 1110, which indicates that this address is a
multicast address. Only 23 bits of the remaining 28 bits are mapped to a MAC address, so five bits of
the multicast IPv4 address are lost. As a result, 32 multicast IPv4 addresses map to the same IPv4
multicast MAC address. Therefore, in Layer 2 multicast forwarding, a device might receive some multicast
data destined for other IPv4 multicast groups. The upper layer must filter such redundant data.
Meaning
Reserved
Interface-local scope
Link-local scope
Subnet-local scope
Admin-local scope
Site-local scope
Unassigned
Organization-local scope
Global scope
8