7
Figure 4 IPv6 multicast format
The following describes the fields of an IPv6 multicast address:
{
0xFF
—The most significant eight bits are 11111111.
{
Flags
—The Flags field contains four bits.
Figure 5 Flags field format
Table 4 Flags field description
Bit Description
0
Reserved, set to 0.
R
•
When set to 0, this address is an IPv6 multicast
address without an embedded RP address.
•
When set to 1, 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, this address is an IPv6 multicast
address not based on a unicast prefix.
•
When set to 1, 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, this address is an IPv6 multicast
address permanently-assigned by IANA.
•
When set to 1, this address is a transient or
dynamically assigned IPv6 multicast address.
{
Scope
—The Scope field contains four bits, which represent 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.
