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.
Group ID (112 bits)
0xFF
Flags
Scope
0
7
11
15
31
0 R P T
