Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 62)

50 Multi-Service IronWare Multicast Configuration Guide
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PIM Sparse
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The infinity | num parameter specifies the number of packets. If you specify infinity, the device
sends packets using the RP indefinitely and does not switch over to the SPT. If you enter a specific
number of packets, the device does not switch over to using the SPT until it has sent the number of
packets you specify using the RP.
Configuring PIM-SM (*,g) forwarding
By default, the device supports only (s,g) hardware routing. This is adequate in network topologies
where there a limited number of multicast flows, and most SPT and RPF paths diverge from the PIM
Last Hop (PIM LH) from the PIM First Hop (PIM FH).
If however, the RPF path from a PIM LH to the PIM RP and the source is the same, the intermediate
devices between RP and LH can be optimized to aggregate multicast flows destined to the same
group address to use a single (*,g) CAM entry, instead of consuming an (s,g) hardware entry for
each flow. This reduces CAM usage as well as the number of IPCs between the interface and
management modules to manage the individual (s,g) states.
For example, where a service provider is provisioning multicast service, with only the route of PIM
RP being visible to customers, and routes to the sources are all default, the (*,g) hardware entry
can help optimize system resources by keeping the traffic on the shared tree.
NOTE
It is recommended to configure the spt-threshold infinity command beginning from the PIM LH
router, then to the intermediate PIM routers and finally to the PIM RP.
Configuration details
To enable this feature, you must explicitly configure the spt-threshold infinity command on all
multicast nodes, as shown in the following example.
Brocade(config)# router pim
Brocade(config-pim-router)# spt-threshold infinity
Syntax: [no] spt-threshold infinity
This configuration option forces PIM-SM to distribute multicast traffic on the share tree only. PIM
devices from RP to LH maintain only (*,g) states, regardless of the source location in the network
topology. PIM LH will not initiate (s,g) SPT switchover, so there are no (s,g) joins generated from LH.
Devices in the share tree, eg, devices downstream from RP, create a (*,g) hardware forwarding
state to switch multicast flows for the group.
Changing the PIM Join and Prune message interval
By default, the device sends PIM Sparse Join or Prune messages every 60 seconds. These
messages inform other PIM Sparse devices about clients who want to become receivers (Join) or
stop being receivers (Prune) for PIM Sparse groups.
NOTE
Use the same Join or Prune message interval on all the PIM Sparse devices in the PIM Sparse
domain. If the devices do not all use the same timer interval, the performance of PIM Sparse can be
adversely affected.
To change the Join or Prune interval, enter commands such as the following.
Brocade(config)# router pim
Brocade(config-pim-router)# message-interval 30
Syntax: [no] message-interval num