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Routing Multicast Traffic

371

Router4 has a network that does not have members, it does have an interface
that does, so it will not send a prune message.

F I G U R E 9 . 1 8

PIM DM pruning

There are four criteria that merit a prune message being sent by a router:

The incoming interface fails the RPF check.

There are no directly connected active group members and no PIM
neighbors (considered a leaf router because it has no downstream PIM
neighbors).

A point-to-point non-leaf router receives a prune request from a
neighbor.

A LAN non-leaf router receives a prune request from another router
and no other router on the segment overrides the prune request.

If any of these criteria are met, a prune request is sent to the PIM neighbor
and the SPT is pruned back.

HostA

HostF

HostB

HostC

HostD HostE

Source for

224.2.125.125

Member
224.2.125.125

Member

224.2.125.125

Router1

Router2

Router3

HostG

Router5

Router4

Prune

message

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