H3C Technologies H3C S12500-X Series Switches - Manual (Page 199)

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• 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.
• The same IPv6 PIM mode must run on the entire network. Otherwise, the multicast distribution tree
cannot be correctly built, causing abnormal multicast forwarding.
Solution
1. Use display ipv6 routing-table to verify that an IPv6 unicast route to the IPv6 multicast source or the
RP is available.
2. Use display ipv6 pim interface to verify IPv6 PIM information on each interface, especially on the
RPF interface. If IPv6 PIM is not enabled on the interfaces, use ipv6 pim dm or ipv6 pim sm to
enable IPv6 PIM-DM or IPv6 PIM-SM for the interfaces.
3. Use display ipv6 pim neighbor to verify that the RPF neighbor is an IPv6 PIM neighbor.
4. Verify that IPv6 PIM and MLD are enabled on the interfaces that directly connect to the IPv6
multicast sources or the receivers.
5. Use display ipv6 pim interface verbose to verify that the same IPv6 PIM mode is enabled on the RPF
interface on a router and the connected interface of the router's RPF neighbor.
6. Use display current-configuration to verify that the same IPv6 PIM mode is enabled on all routers
on the network. For IPv6 PIM-SM, verify that the BSR and C-RPs are correctly configured.
IPv6 multicast data is abnormally terminated on an
intermediate router
Symptom
An intermediate router can receive IPv6 multicast data successfully, but the data cannot reach the
last-hop router. An interface on the intermediate router receives IPv6 multicast data but does not create
an (S, G) entry in the IPv6 PIM routing table.
Analysis
• If an IPv6 multicast forwarding boundary has been configured through the ipv6 multicast boundary
command, and the IPv6 multicast packets are kept from crossing the boundary, IPv6 PIM cannot
create routing entries for the packets.
• If an ACL is defined by the source-policy command, and the IPv6 multicast packets cannot match
the ACL rules, IPv6 PIM cannot create the routing entries for the packets.