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Assume that Host A needs to receive the information a specific IPv6 multicast source S (4001::100/64)
sends to multicast group G (FF3E::101). Router A builds an SPT toward the multicast source. Routers on
the SPT path (Router A and Router D) have generated an (S, G) entry, but Router E, which is not on the
SPT path, does not have multicast routing entries. You can use the
display pim ipv6 routing-table
command to display the PIM routing table information on each router.
For example:
# Display IPv6 PIM multicast routing table information on Router A.
[RouterA] display pim ipv6 routing-table
Total 0 (*, G) entry; 1 (S, G) entry
(4001::100, FF3E::101)
Protocol: pim-ssm, Flag:
UpTime: 00:00:11
Upstream interface: Serial2/0
Upstream neighbor: 1002::2
RPF prime neighbor: 1002::2
Downstream interface(s) information:
Total number of downstreams: 1
1: Ethernet1/1
Protocol: mld, UpTime: 00:00:11, Expires: 00:03:25
# Display IPv6 PIM multicast routing table information on Router D.
[RouterD] display pim ipv6 routing-table
Total 0 (*, G) entry; 1 (S, G) entry
(4001::100, FF3E::101)
Protocol: pim-ssm, Flag: LOC
UpTime: 00:08:02
Upstream interface: Ethernet1/1
Upstream neighbor: NULL
RPF prime neighbor: NULL
Downstream interface(s) information:
Total number of downstreams: 1
1: Serial2/0
Protocol: pim-ssm, UpTime: 00:08:02, Expires: 00:03:25
Troubleshooting IPv6 PIM
This section describes common IPv6 PIM problems and how to troubleshoot them.
A multicast distribution tree cannot be built correctly
Symptom
None of the routers in the network (including routers directly connected with IPv6 multicast sources or
receivers) have multicast forwarding entries. In other words, an IPv6 multicast distribution tree cannot be
correctly built and the receivers cannot receive IPv6 multicast data.
Analysis
•
An IPv6 PIM routing entry is created based on an IPv6 unicast route, whichever IPv6 PIM mode is
running. Multicast works only when unicast does.