3com S7906E 설치 설명서

1-58 

RPF interface and the next hop will be taken as the RPF neighbor. The RPF interface completely 

relies on the existing unicast route, and is independent of PIM. The RPF interface must be 

PIM-enabled, and the RPF neighbor must also be a PIM neighbor. If PIM is not enabled on the 

router where the RPF interface or the RPF neighbor resides, the establishment of a multicast 

distribution tree will surely fail, causing abnormal multicast forwarding. 

z 

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 surely fail, causing abnormal multicast forwarding. 

z 

The same PIM mode must run on the entire network. Otherwise, the establishment of a multicast 

distribution tree will surely fail, causing abnormal multicast forwarding. 

1)  Check unicast routes. Use the display ip routing-table command to check whether a unicast 

route exists from the receiver host to the multicast source. 

2)  Check that PIM is enabled on the interfaces, especially on the RPF interface. Use the display pim 

interface  command to view 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)  Check that the RPF neighbor is a PIM neighbor. Use the display pim neighbor command to view 

the PIM neighbor information. 

4)  Check that PIM and IGMP are enabled on the interfaces directly connecting to the multicast source 

and to the receivers. 

5)  Check that the same PIM mode is enabled on related interfaces. Use the display pim interface 

verbose command to check whether the same PIM mode is enabled on the RPF interface and the 

corresponding interface of the RPF neighbor router. 

6)  Check that the same PIM mode is enabled on all the routers in the entire network. Make sure that 

the same PIM mode is enabled on all the routers: PIM-SM on all routers, or PIM-DM on all routers. 

In the case of PIM-SM, also check that the BSR and RP configurations are correct.  

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. 

z 

If a multicast forwarding boundary has been configured through the multicast boundary 

command, any multicast packet will be kept from crossing the boundary, and therefore no routing 

entry can be created in the PIM routing table. 

z 

In addition, the source-policy command is used to filter received multicast packets. If the multicast 

data fails to pass the ACL rule defined in this command, PIM cannot create the route entry, either. 

1)  Check the multicast forwarding boundary configuration. Use the display current-configuration 

command to check the multicast forwarding boundary settings. Use the multicast boundary 

command to change the multicast forwarding boundary settings.