3Com Switch 4800G 24-Port Configuration Manual page 671

RPs Unable to Join SPT in
PIM-SM
No Unicast Route
Between BSR and C-RPs
in PIM-SM
Solution
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.
2 Check the multicast filter configuration. Use the display current-configuration
command to check the multicast filter configuration. Change the ACL rule defined
in the source-policy command so that the source/group address of the multicast
data can pass ACL filtering.
Symptom
An RPT cannot be established correctly, or the RPs cannot join the SPT to the
multicast source.
Analysis
As the core of a PIM-SM domain, the RPs serve specific multicast groups.
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Multiple RPs can coexist in a network. Make sure that the RP information on all
routers is exactly the same, and a specific group is mapped to the same RP.
Otherwise, multicast forwarding will fail.
If the static RP mechanism is used, the same static RP command must be
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executed on all the routers in the entire network. Otherwise, multicast
forwarding will fail.
Solution
1 Check that a route is available to the RP. Carry out the display ip routing-table
command to check whether a route is available on each router to the RP.
2 Check the dynamic RP information. Use the display pim rp-info command to
check whether the RP information is consistent on all routers.
3 Check the configuration of static RPs. Use the display pim rp-info command to
check whether the same static RP address has been configured on all the routers in
the entire network.
Symptom
C-RPs cannot unicast advertise messages to the BSR. The BSR does not advertise
bootstrap messages containing C-RP information and has no unicast route to any
C-RP. An RPT cannot be established correctly, or the DR cannot perform source
register with the RP.
Analysis
The C-RPs periodically send C-RP-Adv messages to the BSR by unicast. If a C-RP
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has no unicast route to the BSR, the BSR cannot receive C-RP-Adv messages
from that C-RP and the bootstrap message of the BSR will not contain the
information of that C-RP.
In addition, if the BSR does not have a unicast router to a C-RP, it will discard
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the C-RP-Adv messages from that C-RP, and therefore the bootstrap messages
of the BSR will not contain the information of that C-RP.
Troubleshooting PIM Configuration 671