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3
PIM Dense
FIGURE 4
Pruning leaf nodes from a multicast tree
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 Group
Member Member
...
Group
Member
R2
R1
R3
R4
Prune Message
sent to upstream router (R4)
R5
R6
Leaf Node
(No Group Members)
... ...
Intermediate Node
(No Group Members)
Group Group
Member Member
229.225.0.1
Group
Member
Grafts to a multicast tree
A PIM device restores pruned branches to a multicast tree by sending graft messages towards the
upstream device. Graft messages start at the leaf node and travel up the tree, first sending the
message to its neighbor upstream device.
In the example above, if a new 229.255.0.1 group member joins on device R6, which was
previously pruned, a graft is sent upstream to R4. Since the forwarding state for this entry is in a
prune state, R4 sends a graft to R1. Once R4 has joined the tree, R4 along with R6 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
The Brocade device supports only PIM V2. PIM DM V2 sends messages to the multicast address
224.0.0.13 (ALL-PIM-ROUTERS) with protocol number 103.
Configuring PIM DM
NOTE
This section describes how to configure the “dense” mode of PIM, described in RFC 1075. Refer to
“Configuring PIM Sparse” on page 86 for information about configuring PIM Sparse.
74 FastIron Ethernet Switch IP Multicast Configuration Guide
53-1002638-02