HP FlexFabric 5950 series Configuration Manual page 182

As shown in
on PIM-SM routers that assume different roles function differently.
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MSDP peers created on RPs:
Source-side MSDP peer—MSDP peer closest to the multicast source, such as RP 1. The

source-side RP creates and sends SA messages to its remote MSDP peer to notify the
MSDP peer of the locally registered multicast source information.
A source-side MSDP peer must be created on the source-side RP. Otherwise, it cannot
advertise the multicast source information out of the PIM-SM domain.
Receiver-side MSDP peer—MSDP peer closest to the receivers, typically the receiver-side

RP, such as RP 3. After receiving an SA message, the receiver-side MSDP peer resolves
the multicast source information carried in the message. Then, it joins the SPT rooted at the
multicast source across the PIM-SM domains. When multicast data from the multicast
source arrives, the receiver-side MSDP peer forwards the data to the receivers along the
RPT.
Intermediate MSDP peer—MSDP peer with multiple remote MSDP peers, such as RP 2.

An intermediate MSDP peer forwards SA messages received from one remote MSDP peer
to other remote MSDP peers. It acts as a relay for forwarding multicast source information.
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MSDP peers created on PIM-SM routers that are not RPs:
Router A and Router B are MSDP peers on multicast routers that are not RPs. Such MSDP
peers only forward SA messages.
In a PIM-SM network using the BSR mechanism, the RP is dynamically elected from C-RPs. A
PIM-SM network typically has multiple C-RPs to ensure network robustness. Because the RP
election result is unpredictable, MSDP peering relationships must be built between all C-RPs to
always keep the winning C-RP on the MSDP interconnection map. Losing C-RPs assume the role of
common PIM-SM routers on this map.
Inter-domain multicast delivery through MSDP
As shown in
learned the existence of Source through multicast source registration. RPs in PIM-SM 2 and PIM-SM
3 also seek the location of Source so that multicast traffic from Source can be sent to their receivers.
MSDP peering relationships must be established between RP 1 and RP 3 and between RP 3 and RP
2.
Figure 60, an MSDP peer can be created on any PIM-SM router. MSDP peers created
Figure 61, an active source (Source) exists in the domain PIM-SM 1, and RP 1 has
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