Troubleshooting Pim; A Multicast Distribution Tree Cannot Be Correctly Built - HP 5920 series Configuration Manual

# Display RP information on Switch D.
[SwitchD] display pim rp-info
BSR RP information:
Scope: non-scoped
Group/MaskLen: 224.0.0.0/4
RP address
10.110.9.1
Scope: 239.0.0.0/8
Group/MaskLen: 239.0.0.0/8
RP address
10.110.5.2 (local)
# Display RP information on Switch F.
[SwitchF] display pim rp-info
BSR RP information:
Scope: non-scoped
Group/MaskLen: 224.0.0.0/4
RP address
10.110.9.1 (local)

Troubleshooting PIM

A multicast distribution tree cannot be correctly built

Symptom
None of the routers in the network (including routers directly connected with multicast sources or
receivers) have multicast forwarding entries. In other words, a multicast distribution tree cannot be
correctly built and the receiver hosts cannot receive multicast data.
Analysis
• On a PIM-DM enabled network, multicast data is flooded from the router that directly connects to
the multicast source to the routers that directly connects to the receivers. When the multicast data is
flooded to a router, the router creates an (S, G) entry only if it has a route to the multicast source. If
the router does not have a route to the multicast source, or if PIM-DM is not enabled on the RPF
interface toward the multicast source, the router cannot create an (S, G) entry.
On a PIM-SM enabled network, when a router wants to join the SPT, the router creates an (S, G)
•
entry only if it has a route to the multicast source. If the router does not have a route to the multicast
source, or if PIM-SM is not enabled on the RPF interface toward the multicast source, the router
cannot create an (S, G) entries.
When a multicast router receives a multicast packet, it looks up the existing unicast routing table for
•
the optimal route to the packet source. The outgoing interface of this route act as the RPF interface
and the next hop acts the RPF neighbor. The RPF interface completely relies on the existing unicast
route and is independent of PIM. The RPF interface must be enabled with PIM, and the RPF neighbor
must be a PIM neighbor. If PIM is not enabled on the RPF interface or the RPF neighbor, the multicast
distribution tree cannot be built correctly, causing abnormal multicast forwarding.
Because a hello message does not carry PIM mode information, a PIM router cannot identify what
•
PIM mode its PIM neighbor is running. If the RPF interface on a router and the connected interface
Priority HoldTime
192 150
Priority HoldTime
192 150
Priority HoldTime
192 150
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Uptime Expires
00:03:42 00:01:48
Uptime Expires
00:06:54 00:02:41
Uptime Expires
00:00:32 00:01:58