Dell PowerConnect B-RX Configuration Manual page 675

When a node on the multicast delivery tree has all of its downstream branches (downstream
interfaces) in the prune state, a prune message is sent upstream. In the case of R4, if both R5 and
R6 are in a prune state at the same time, R4 becomes a leaf node with no downstream interfaces
and sends a prune message to R1. With R4 in a prune state, the resulting multicast delivery tree
would consist only of leaf nodes R2 and R3.
FIGURE 90
BigIron RX Series Configuration Guide
53-1002253-01
Transmission of multicast packets from the source to host group members
229.225.0.1
Group
Group
Member
Member
R2
Leaf Node
R5
Leaf Node
(No Group Members)
Intermediate Node
(No Group Members)
Video Conferencing
Server
(207.95.5.1, 229.225.0.1)
(Source, Group)
R1
R4
...
Group
Member
229.225.0.1
23
PIM dense
229.225.0.1
Group Group Group
Member Member
Member
...
R3
R6
Leaf Node
...
Group Group
Member Member
599