Troubleshooting Pim Configuration; Failure Of Building A Multicast Distribution Tree Correctly - HP A5500 SI Switch Series Configuration Manual

Total number of downstreams: 1
1: Vlan-interface100
The information on Switch B and Switch C is similar to that on Switch A.
# View the PIM routing table information on Switch D.
[SwitchD] display pim routing-table
VPN-Instance: public net
Total 0 (*, G) entry; 1 (S, G) entry
(10.110.5.100, 232.1.1.1)
Protocol: pim-ssm, Flag: LOC
UpTime: 00:12:05
Upstream interface: Vlan-interface300
Upstream neighbor: NULL
RPF prime neighbor: NULL
Downstream interface(s) information:
Total number of downstreams: 1
1: Vlan-interface105

Troubleshooting PIM configuration

Failure of building a multicast distribution tree correctly

Symptom
None of the routers in the network (including routers directly connected with multicast sources and
receivers) have multicast forwarding entries. A multicast distribution tree cannot be built correctly and
clients cannot receive multicast data.
Analysis
When PIM-DM runs on the entire network, multicast data is flooded from the first hop router
•
connected with the multicast source to the last hop router connected with the clients. When the
multicast data is flooded to a router, regardless of which router it is, the router creates (S, G) entries
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 router's RPF interface to the multicast source, the router
cannot create (S, G) entries.
When PIM-SM runs on the entire network and when a router will join the SPT, the router creates (S,
•
G) entries 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 router's RPF interface to the multicast source,
the router cannot create (S, G) entries.
When a multicast router receives a multicast packet, it searches the existing unicast routing table for
•
the optimal route to the RPF check object. The outgoing interface of this route will act as the RPF
interface and the next hop will be taken as the RPF neighbor. The RPF interface completely relies on
the existing unicast route and is independent of PIM. The RPF interface must be PIM-enabled, and
the RPF neighbor must also be a PIM neighbor. If PIM is not enabled on the router where the RPF
interface or the RPF neighbor resides, the establishment of a multicast distribution tree will surely
fail, causing abnormal multicast forwarding.
Protocol: igmp, UpTime: 00:13:25, Expires: 00:03:25
Protocol: pim-ssm, UpTime: 00:12:05, Expires: 00:03:25
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