spt-threshold

Each IPv6 PIM Sparse router that is a DR for an IPv6 receiver calculates a short path tree (SPT) towards the source of the IPv6 multicast traffic. The first time the device configured as an IPv6 PIM router receives a packet for an IPv6 group, it sends the packet to the RP for that group, which in turn will forward it to all the intended DRs that have registered with the RP. The first time the device is a recipient, it receives a packet for an IPv6 group and evaluates the shortest path to the source and initiates a switchover to the SPT. Once the device starts receiving data on the SPT, the device proceeds to prune itself from the RPT.

You can change the number of packets the device receives using the RP before switching to using 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.

The no form of the command restores the default behavior. That is, the device switches from the RP to the SPT after receiving the first packet for a given IPv6 PIM Sparse group. The device maintains a separate counter for each IPv6 PIM Sparse source-group pair.