HP ProCurve Series 6120 Blade Switches IPv6 Configuration Guide

IPv6 Addressing
Multicast Application to IPv6 Addressing
IPv6 Multicast Address Format
The multicast address format has three principal sections in the leading 16
bits:
■ identifier: ff (bits 1-8)
■ flags: 0xxx (bits 9-12)
■ scope: 0001 - 1110 (bits 13-16)
For related information, refer to RFC 4291.
Multicast Group Identification
Multicast ID, Flags and Scope (16 bits) Group Identifier (112 bits)
1111 1111 0xxx xxxx :
x...x : x...x : x...x : x...x : x...x : x...x : x...x
■ multicast identifier: The first eight high-order bits, set to ff, identify the
address as multicast.
■ multicast flags: Bits 9-12 are multicast flags that provide additional
information about the multicast address, as follows:
Bit ID Options Use
9 0 reserved
10 (R) 0 multicast address without PIM-SM rendezvous point
1 multicast address with PIM-SM rendezvous point
11 (P) 0 multicast address without prefix information from the
originating network
1 multicast address with prefix information from the originating
network
12 (T) 0 multicast address is permanent (well-known, and not
restricted by scope value)
1 multicast address is temporary (and used only within an
identified scope)
■ multicast scope: Bits 13-16 set boundaries on multicast traffic distribu-
tion, such as the interface defined by the link-local unicast address of an
area, or the network boundaries of an organization. Because IPv6 uses
multicast technology in place of the broadcast technology used in IPv4,
the multicast scope field also controls the boundaries for broadcast-type
traffic sent in multicast packets.
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