# Switching to an SPT for PIM Sparse Mode

PIM sparse mode initiates multicast 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 can be more efficient than multicasting over a shared tree (see PIM Sparse Mode).

ipv6 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 to configure PIM to switch to an SPT when a source starts sending multicast messages.
- Example
  host1(config)#ipv6 pim spt-threshold 4
- Use the no version to restore the default, 0.
- See ipv6 pim spt-threshold.