HP MSR2000/3000/4000 Router Series IP Multicast Configuration Guide

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# Display IPv6 PIM multicast routing table information on Router D.
[RouterD] display ipv6 pim 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: Ethernet1/2
Protocol: pim-ssm, UpTime: 00:08:02, Expires: 00:03:25
Troubleshooting IPv6 PIM
A multicast distribution tree cannot be correctly built
Symptom
An IPv6 multicast distribution tree cannot be correctly built because there are no IPv6 multicast
forwarding entries established on the routers (including routers directly connected with multicast sources
or receivers) in a IPv6 PIM network.
Analysis
• On an IPv6 PIM-DM enabled network, IPv6 multicast data is flooded from the router that directly
connects to the IPv6 multicast source to the routers that directly connects to the receivers. When the
IPv6 multicast data is flooded to a router, the router creates an (S, G) entry only if it has a route to
the IPv6 multicast source. If the router does not have a route to the IPv6 multicast source, or if IPv6
PIM-DM is not enabled on the RPF interface toward the IPv6 multicast source, the router cannot
create an (S, G) entry.
• On an IPv6 PIM-SM enabled network, when a router wants to join the SPT, the router creates an (S,
G) entry only if it has a route to the IPv6 multicast source. If the router does not have a route to the
IPv6 multicast source, or if IPv6 PIM-SM is not enabled on the RPF interface toward the IPv6
multicast source, the router cannot create an (S, G) entry.
• When a multicast router receives an IPv6 multicast packet, it looks up the existing IPv6 unicast
routing table for the optimal route to the packet source. The outgoing interface of this route act as
the RPF interface and the next hop acts the RPF neighbor. The RPF interface completely relies on the
existing IPv6 unicast route and is independent of IPv6 PIM. The RPF interface must be enabled with
IPv6 PIM, and the RPF neighbor must be an IPv6 PIM neighbor. If IPv6 PIM is not enabled on the RPF
interface or the RPF neighbor, the multicast distribution tree cannot be correctly built, causing
abnormal multicast forwarding.
• Because a hello message does not carry IPv6 PIM mode information, an IPv6 PIM router cannot
identify what IPv6 PIM mode its IPv6 PIM neighbor is running in. If the RPF interface on a router and
the connected interface of the router's RPF neighbor operate in different IPv6 PIM modes, the
multicast distribution tree cannot be correctly built, causing abnormal multicast forwarding.