HPE 5820X Series, Configuration Manual

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IPv6 BIDIR-PIM is suitable for networks with dense multicast sources and dense receivers.
The operating mechanism of IPv6 BIDIR-PIM is summarized as follows:
•
Neighbor discovery
•
RP discovery
•
DF election
•
Bidirectional RPT building
Neighbor discovery
IPv6 BIDIR-PIM uses the same neighbor discovery mechanism as IPv6 PIM-SM does. For more
information, see "
Neighbor discovery ."
RP discovery
IPv6 BIDIR-PIM uses the same RP discovery mechanism as IPv6 PIM-SM does. For more
information, see "
RP discovery ."
In IPv6 PIM-SM, an RP must be specified with a real IPv6 address. In IPv6 BIDIR-PIM, however, an
RP can be specified with a virtual IPv6 address, which is called the RPA. The link corresponding to
the RPA's subnet is called the RPL. All interfaces connected to the RPL can act as RPs, which back
up one another.
NOTE:
In IPv6 BIDIR-PIM, an RPF interface is the interface pointing to an RP, and an RPF neighbor is the
address of the next hop to the RP.
DF election
On a network segment with multiple multicast routers, the same multicast packets might be
forwarded to the RP repeatedly. To address this issue, IPv6 BIDIR-PIM uses a DF election
mechanism to elect a unique designated forwarder (DF) for each RP on every network segment
within the IPv6 BIDIR-PIM domain. Only the DF to forward multicast data to the RP.
NOTE:
DF election is not necessary for an RPL.
Figure 122 DF election
As shown in Figure 122 , without the DF election mechanism, both Router B and Router C can
receive multicast packets from Route A, and they might both forward the packets to downstream
Ethernet
Router B Router C
Router A
IPv6 Multicast packets
DF election message
RP
Source
Router D Router E