Edge Routers - HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual

Configuring Multicast Support with PIM-SM
Overview
The (*, G) entry
The (S, G) entry
for the SP tree
The (S, G) entry
for the RP tree
11-12
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
(*, 239.255.255.1), 01:10:32/00:00:00, RP 10.1.1.1, Flags: SJ
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
fr 1.2, Forward, 00:12:11/00:02:09
fr 1.3, Forward, 00:44:59/00:02:13
(192.168.100.2, 239.255.255.1), 00:01:43/00:03:30, Flags: ST
Incoming interface: fr 1.3, RPF nbr 10.3.3.2
Outgoing interface list:
fr 1.2, Pruned, 00:00:43/00:01:37
(192.168.100.2, 239.255.255.1), 00:00:43/00:02:47, Flags: SJR
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list: Null
Figure 11-4. Multicast Routing Table for an RP

Edge Routers

Only edge routers that are directly connected to multicast hosts can initiate
the transition to an SP tree. Intervening routers can join an SP tree, but only
when they receive a join from a downstream neighbor, not when they receive
multicast traffic.
When a ProCurve Secure Router receives a multicast packet from a source, it
creates an (S, G) entry, taking the source from the packet's source address
and the group address from its destination address. An edge router connects
directly to a member of the group, so it sets the entry's C bit.
The router then uses RPF to determine which interface connects most directly
to the source; this interface becomes the (S, G) entry's incoming interface. If
this interface is different from the interface through which the router connects
to the RP (and if the entry's C bit is set), then the router switches to the SP
tree and prunes itself from the RP tree.
After it receives a multicast, an edge router follows this process to switch to
the SP tree. (See Figure 11-5.)
The RP will join the SP
tree when a source
registers with it.
All downstream routers have left
the RP tree. When the (S, G)
entry times out, the router will
prune itself from the SP tree.