3Com Switch 8800 Advanced Software V5 Configuration Guide

Troubleshooting PIM Configuration 607
No Unicast Route
Between BSR and C-RPs
in PIM-SM
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
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 device to a C-RP, it will discard
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.
■ The RP is the core of a PIM-SM domain. Make sure that the RP information on
all devices is exactly the same, a specific group G is mapped to the same RP,
and unicast routes are available to the RP.
Solution
1 Check whether routes to C-RPs, the RP and the BSR are available. Carry out
the display ip routing-table command to check whether routes are
available on each device to the RP and the BSR, and whether a route is
available between the RP and the BSR. Make sure that each C-RP has a
unicast route to the BSR, the BSR has a unicast route to each C-RP, and all
the devices in the entire network have a unicast route to the RP.
2 Check the RP and BSR information. PIM-SM needs the support of the RP
and BSR. Use the display pim bsr-info command to check whether the BSR
information is available on each device, and then use the display pim
rp-info command to check whether the RP information is correct.
3 View PIM neighboring relationships. Use the display pim neighbor
command to check whether the normal PIM neighboring relationships
have been established among the devices.