3Com Switch 8800 Advanced Software V5 Configuration Guide

604 CHAPTER 42: PIM CONFIGURATION
D for example) generates (S, G) entries, while Switch E, which is not on the SPT
path does not have multicast routing entries. You can use the display pim
routing-table command to view the PIM routing table information on each
switch. For example:
# View the PIM routing table information on Switch A.
<SwitchA> 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: Vlan-interface101
Upstream neighbor: 192.168.1.2,
RPF prime neighbor: 192.168.1.2
Downstream interface(s) information:
Total number of downstreams: 1
1: Vlan-interface100
Protocol: pim-ssm, UpTime: 00: 13: 25, Expires: -
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:
UpTime: 00: 12: 05
Upstream interface: Vlan-interface300
Upstream neighbor: 10.110.5.100,
RPF prime neighbor: 10.110.5.100
Downstream interface(s) information:
Total number of downstreams: 1
1: Vlan-interface105
Protocol: pim, UpTime: 00: 12: 05, Expires: 00: 03: 25
Troubleshooting PIM
Configuration
Failure of Building a
Multicast Distribution
Tree Correctly
Symptom
None of the devices in the network (including devices 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
first hop device connected with the multicast source to the last hop device
connected with the clients along the SPT. When the multicast data is flooded to