Operation Manual – Multicast
H3C S3600 Series Ethernet Switches-Release 1510 Chapter 7 PIM Configuration
7-6
Figure 7-3 Diagram for DR election
Each router on the shared network sends Hello messages with the DR priority option to
each other. The router with the highest DR priority is elected as the DR in the network.
If the priority is the same, the router with the highest IP address is elected as the DR.
When DR fails, the received Hello messages will time out. A new DR election
procedure will be triggered among neighboring routers.
Note:
z S3600 Series Ethernet Switches do not support DR priority. In a network containing
S3600 Series Ethernet Switches, the DR is elected by IP addresses.
z In a PIM-SM network, DR mainly serves as the querier of IGMPv1.
III. RP discovery
RP is the core router in a PIM-SM domain. The shared tree established based on the
multicast routing information is rooted in RP. There is a mapping relationship between
the multicast group and RP. One multicast group is mapped to one RP, and multiple
multicast groups can be mapped to the same RP.
In a small and simple network, there is only little multicast information. One RP is
enough for information forwarding. In this case, you can statically specify the position of
RP in each router in the SM domain.
However, a PIM-SM network is normally of very large scale and RP forwards a lot of
multicast information. In order to reduce the workload of RP and optimize the topology
of the shared tree, different multicast groups must have different RPs. In this case, RP
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