Join-Prune Messages; State Refreshes; Rendezvous Points - Cisco Nexus 7000 Series Configuration Manual

Configuring PIM and PIM6
For added security, you can configure an MD5 hash value that the PIM software uses to authenticate PIM
hello messages with PIM neighbors.
For information about configuring hello message authentication, see Configuring PIM or PIM6 Sparse Mode.

Join-Prune Messages

When the DR receives an IGMP membership report message from a receiver for a new group or source, the
DR creates a tree to connect the receiver to the source by sending a PIM join message out the interface toward
the rendezvous point (ASM or Bidir mode) or source (SSM mode).The rendezvous point (RP) is the root of
a shared tree, which is used by all sources and hosts in the PIM domain in the ASM or the Bidir mode. SSM
does not use an RP but builds a shortest path tree (SPT) that is the lowest cost path between the source and
the receiver.
When the DR determines that the last host has left a group or source, it sends a PIM prune message to remove
the path from the distribution tree.
The routers forward the join or prune action hop by hop up the multicast distribution tree to create (join) or
tear down (prune) the path.
Note
In this publication, the terms "PIM join message" and "PIM prune message" are used to simplify the action
taken when referring to the PIM join-prune message with only a join or prune action.
Join-prune messages are sent as quickly as possible by the software. You can filter the join-prune messages
by defining a routing policy. For information about configuring the join-prune message policy, see Configuring
PIM or PIM6 Sparse Mode.

State Refreshes

PIM requires that multicast entries are refreshed within a 3.5-minute timeout interval. The state refresh ensures
that traffic is delivered only to active listeners, and it keeps routers from using unnecessary resources.
To maintain the PIM state, the last-hop DR sends join-prune messages once per minute. State creation applies
to both (*, G) and (S, G) states as follows:
• (*, G) state creation example—An IGMP (*, G) report triggers the DR to send a (*, G) PIM join message
• (S, G) state creation example—An IGMP (S, G) report triggers the DR to send an (S, G) PIM join message
If the state is not refreshed, the PIM software tears down the distribution tree by removing the forwarding
paths in the multicast outgoing interface list of the upstream routers.

Rendezvous Points

A rendezvous point (RP) is a router that you select in a multicast network domain that acts as a shared root
for a multicast shared tree. You can configure as many RPs as you like, and you can configure them to cover
different group ranges.
toward the RP.
toward the source.
Cisco Nexus 7000 Series NX-OS Multicast Routing Configuration Guide
Join-Prune Messages
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