736 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
PIM Dense
25
FIGURE 121 Pruning leaf nodes from a multicast tree
Grafts to a multicast Tree
A PIM switch restores pruned branches to a multicast tree by sending graft messages towards the
upstream switch. Graft messages start at the leaf node and travel up the tree, first sending the
message to its neighbor upstream switch.
In the example above, if a new 229.255.0.1 group member joins on switch S6, which was
previously pruned, a graft is sent upstream to S4. Since the forwarding state for this entry is in a
prune state, S4 sends a graft to S1. Once S4 has joined the tree, S4 and S6 once again receive
multicast packets.
Prune and graft messages are continuously used to maintain the multicast delivery tree. No
configuration is required on your part.
PIM DM versions
Dell PowerConnect devices support PIM DM V1 and V2. The default is V2. You can specify the
version on an individual interface basis.
The primary difference between PIM DM V1 and V2 is the methods the protocols use for
messaging:
• PIM DM V1 – uses the Internet Group Management Protocol (IGMP) to send messages
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229.225.0.1
Group
Member
Group
Member
Video Conferencing
Server
(207.95.5.1, 229.225.0.1)
(Source, Group)
229.225.0.1
Group
Member
Group
Member
Group
Member
Group
Member
Group
Member
Group
Member
229.225.0.1
Leaf Node
(No Group Members)
Intermediate Node
(No Group Members)
R2
R1
R3
R4
R5
R6
Prune Message
sent to upstream router (R4)
