Switching to an SPT for PIM Sparse Mode

PIM sparse mode initiates multicasting using a shared tree. You can configure PIM sparse mode to switch to an SPT when a source starts sending multicast messages, or you can prevent PIM sparse mode from switching to an SPT. Multicasting over an SPT might be more efficient than multicasting over a shared tree. (See PIM Sparse Mode.)

ip pim spt-threshold

Use to specify when PIM sparse mode switches from a shared tree to an SPT.
Specify a nonzero integer or the keyword infinity to prevent PIM sparse mode from switching to an SPT.
Specify a value of 0 (default) to configure PIM to switch to an SPT when a source starts sending multicast messages.
Example
host1(config)#ip pim spt-threshold 4
Use the no version to restore the default value, 0.
See ip pim spt-threshold.