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• Because a hello message does not carry the PIM mode information, a router running PIM is unable
to know what PIM mode its PIM neighbor is running. If different PIM modes are enabled on the RPF
interface and on the corresponding interface of the RPF neighbor router, the establishment of a
multicast distribution tree will fail, causing abnormal multicast forwarding.
• The same PIM mode must run on the entire network. Otherwise, the establishment of a multicast
distribution tree will fail, causing abnormal multicast forwarding.
Solution
1. Verify unicast routes. Use the display ip routing-table command to determine whether a unicast
route exists from the receiver host to the multicast source.
2. Verify that PIM is enabled on the interfaces, especially on the RPF interface. Use the display pim
interface command to determine the PIM information on each interface. If PIM is not enabled on the
interface, use the pim dm or pim sm command to enable PIM-DM or PIM-SM.
3. Verify that the RPF neighbor is a PIM neighbor. Use the display pim neighbor command to view the
PIM neighbor information.
4. Verify that PIM and IGMP are enabled on the interfaces that are directly connected to the multicast
source and to the receivers.
5. Verify that the same PIM mode is enabled on related interfaces. Use the display pim interface
verbose command to determine whether the same PIM mode is enabled on the RPF interface and
the corresponding interface of the RPF neighbor router.
6. Verify that the same PIM mode—PIM-SM or PIM-DM—is enabled on all the routers in the entire
network. Be sure that the same PIM mode is enabled on all the routers. In the case of PIM-SM, also
verify that the BSR and RP configurations are correct.
Multicast data abnormally terminated on an intermediate router
Symptom
An intermediate router can receive multicast data successfully, but the data cannot reach the last hop
router. An interface on the intermediate router receives data but no corresponding (S, G) entry is created
in the PIM routing table.
Analysis
• If a multicast forwarding boundary has been configured through the multicast boundary command,
any multicast packet will be kept from crossing the boundary, and no routing entry can be created
in the PIM routing table.
• In addition, the source-policy command filters received multicast packets. If the multicast data fails
to pass the ACL defined in this command, PIM cannot create the route entry either.
Solution
1. Verify the multicast forwarding boundary configuration. Use the display current-configuration
command to determine the multicast forwarding boundary settings. Use the multicast boundary
command to change the multicast forwarding boundary settings.
2. Verify the multicast filter configuration. Use the display current-configuration command to determine
the multicast filter configuration. Change the ACL defined in the source-policy command so that the
source/group address of the multicast data can pass ACL filtering.
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