HP 6125XLG Ip Multicast Configuration Manual page 288

Figure 87 DR election
As shown in
1. The routers on the shared-media LAN send hello messages to one another. The hello messages
contain the priority for DR election. The router with the highest DR priority is elected as the DR.
2. The router with the highest IPv6 link-local address wins the DR election under one of the following
conditions:
All the routers have the same DR election priority.
a.
A router does not support carrying the DR-election priority in hello messages.
b.
If the DR fails, its IPv6 PIM neighbor lifetime expires, and the other routers initiate a new DR election.
RP discovery
An RP is the core of an IPv6 PIM-SM domain. For a small-sized, simple network, one RP is enough for
multicast forwarding throughout the network. In this case, you can specify a static RP on each router in
the IPv6 PIM-SM domain. However, in an IPv6 PIM-SM network that covers a wide area, a huge amount
of IPv6 multicast data is forwarded by the RP. To lessen the RP burden and optimize the topological
structure of the RPT, you can configure multiple candidate-RPs (C-RPs) in an IPv6 PIM-SM domain. An RP
is dynamically elected from the C-RPs by the bootstrap mechanism. An elected RP provides services for
a different IPv6 multicast group. For this purpose, you must configure a bootstrap router (BSR). A BSR
serves as the administrative core of an IPv6 PIM-SM domain. An IPv6 PIM-SM domain has only one BSR,
but can have multiple candidate-BSRs (C-BSRs) so that, if the BSR fails, a new BSR can be automatically
elected from the C-BSRs and avoid service interruption.
NOTE:
An RP can provide services for multiple IPv6 multicast groups, but an IPv6 multicast group only uses one
•
RP.
• A device can act as a C-RP and a C-BSR at the same time.
As shown in
to the BSR. An advertisement message contains the address of the advertising C-RP and the IPv6 multicast
group range to which it is designated. The BSR collects these advertisement messages and organizes the
C-RP information into an RP-set, which is a database of mappings between IPv6 multicast groups and RPs.
Figure 87, the DR election process is as follows:
Figure 88, each C-RP periodically unicasts its advertisement messages (C-RP-Adv messages)
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