Troubleshooting Pim Configuration; Failure Of Building A Multicast Distribution Tree Correctly - 3Com MSR 50 Series Configuration Manual

Troubleshooting PIM
Configuration
Failure of Building a
Multicast Distribution
Tree Correctly
[RouterA] 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:
UpTime: 00:13:25
Upstream interface: Serial2/0
Upstream neighbor: 192.168.1.2
RPF prime neighbor: 192.168.1.2
Downstream interface(s) information:
Total number of downstreams: 1
1: Ethernet1/0
Protocol: igmp, UpTime: 00:13:25, Expires: 00:03:25
The information on Router B and Router C is similar to that on Router A.
# View the PIM routing table information on Router D.
[RouterD] 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: Ethernet1/0
Upstream neighbor: NULL
RPF prime neighbor: NULL
Downstream interface(s) information:
Total number of downstreams: 1
1: Serial2/0
Protocol:
Symptom
None of the routers in the network (including routers directly connected with
multicast sources and receivers) has multicast forwarding entries. That is, 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
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first hop router connected with the multicast source to the last hop router
connected with the clients along the SPT. When the multicast data is flooded to
a router, no matter which router is, it 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 is to join the SPT,
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the router creates (S, G) entries only if it has a route to the multicast source. If

Troubleshooting PIM Configuration

pim-ssm, UpTime: 00:12:05, Expires: 00:03:25
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