HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual page 586

Configuring Multicast Support with PIM-SM
Troubleshooting PIM-SM
N o t e
(*, G) entry for the
RP tree
Group address
11-58
5. If the multicast routing table does have an entry for the group in question,
view the list of outgoing interfaces in this entry. If the local interface that
connects to the network experiencing the problems is not in this list, then
the router will not forward multicasts to it.
The multicast routing table may include both a (*, G) and an (S, G) entry
for the same group. The router matches packets to the (S, G) entry first,
so this is the entry with the outgoing interface list that you should search.
Typically, an interface listed for an IGMP group should be in the outgoing
interface list for the multicast routing table entry for that group. One
reason that interface would not be in the list is that another router in a
multi-access network is responsible for forwarding multicasts for that
group. The local router has lost the assert.
Figure 11-23 shows the multicast routing table for a router in this situation.
ProCurve# show ip mroute
IP Multicast Routing Table
Flags: S - Sparse, C - Connected, P - Pruned, J - Join SPT, T - SPT-
bit Set,
F - Register, R - RP-bit Set
Timers: Uptime/Expires
(*, 233.255.1.1), 00:11:08/00:00:00, RP 10.3.3.2, Flags: SCP
Incoming interface: fr 1.1, RPF nbr 10.2.2.1
Outgoing interface list:
eth 0/1, Pruned, 00:11:08/00:02:39
The local router lost the assert, so
it does not forward multicasts
through this interface.
Figure 11-23. Interface Pruned From a Multicast Routing Table Entry
6. If the incoming interface for the multicast routing table entry is null, the
router will drop any multicasts it receives for that group. The incoming
interface is legitimately null when the local router is the RP for the group.
In this case, however, as soon as a source begins to transmit multicasts
for the group, the router should add an (S, G) entry with the incoming
interface set to the interface through which the router connects to the
source. A (*, G) entry in an RP's multicast routing table should be marked
with the J bit to indicated that the RP is allowed to join an SP tree. (See
Figure 11-24).
The router will
prune itself
from the RP tree