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Troubleshooting IPv6 PIM configuration
Failure to build a multicast distribution tree correctly
Symptom
None of the routers in the network (including routers directly connected with IPv6 multicast sources and
receivers) have IPv6 multicast forwarding entries. That is, a multicast distribution tree cannot be built
correctly and clients 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.
• IPv6 PIM must be enabled on the RPF interface. An RPF neighbor must be an IPv6 PIM neighbor as
well. If IPv6 PIM is not enabled on the RPF interface or the RPF neighbor, the establishment of a
multicast distribution tree will fail, resulting in abnormal multicast forwarding.
• IPv6 PIM requires that the same IPv6 PIM mode (namely, DM or SM) must run on the entire network.
Otherwise, the establishment of a multicast distribution tree will fail, resulting in abnormal multicast
forwarding.
Solution
1. Use the display ipv6 routing-table command to verify that a unicast route exists to the IPv6
multicast source or the RP.
2. Use the display pim ipv6 interface command to verify that the RPF interface is IPv6 PIM enabled.
If IPv6 PIM is not enabled on the interface, use the pim ipv6 dm or pim ipv6 sm command to enable
IPv6 PIM.
3. Use the display pim ipv6 neighbor command to verify that the RPF neighbor is an IPv6 PIM
neighbor.
4. Verify that IPv6 PIM and MLD are enabled on the interfaces that are directly connected to the IPv6
multicast source and to the receiver.
5. Use the display pim ipv6 interface verbose command to verify that the same PIM mode is enabled
on the RPF interface and the corresponding interface of the RPF neighbor router.
6. Use the display current-configuration command to verify that the same IPv6 PIM mode is enabled
on all the routers in the entire network. Make sure that the same IPv6 PIM mode is enabled on all
the routers: IPv6 PIM-SM on all routers, or IPv6 PIM-DM on all routers.
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