Multiple sources sending to groups use the shared tree.
Benefit of Preventing or Delaying the Use of the Shortest-Path Tree
The switch from shared to source tree happens upon the arrival of the first data packet at the last hop device
(Router C in Benefit of Preventing or Delaying the Use of the Shortest-Path Tree, on page 333). This switch
occurs because the ip pim spt-threshold command controls that timing, and its default setting is 0 kbps.
The shortest-path tree requires more memory than the shared tree, but reduces delay. You might want to
prevent or delay its use to reduce memory requirements. Instead of allowing the leaf device to move to the
shortest-path tree immediately, you can prevent use of the SPT or specify that the traffic must first reach a
threshold.
You can configure when a PIM leaf device should join the shortest-path tree for a specified group. If a source
sends at a rate greater than or equal to the specified kbps rate, the device triggers a PIM Join message toward
the source to construct a source tree (shortest-path tree). If the infinity keyword is specified, all sources for
the specified group use the shared tree, never switching to the source tree.
How to Optimize PIM Sparse Mode in a Large IP Multicast
Deployment
Optimizing PIM Sparse Mode in a Large Deployment
Consider performing this task if your deployment of IP multicast is large.
Steps 3, 5, and 6 in this task are independent of each other and are therefore considered optional. Any one of
these steps will help optimize PIM sparse mode. If you are going to perform Step 5 or 6, you must perform
Step 4. Step 6 applies only to a designated router; changing the PIM query interval is only appropriate on
redundant routers on the edge of the PIM domain.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ip pim register-rate-limit rate
4.
ip pim spt-threshold {kbps| infinity}[group-list access-list]
5.
interface type number
6.
ip pim query-interval period [msec]
DETAILED STEPS
PurposeCommand or Action
Enables privileged EXEC mode.enable
Step 1
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3.6E (Catalyst 3850 Switches)
OL-32598-01 333
IP Multicast Optimization: Optimizing PIM Sparse Mode in a Large IP Multicast Deployment
How to Optimize PIM Sparse Mode in a Large IP Multicast Deployment
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