The set protocols pim spt-switchover command configures SPT switchover on a per-group basis, allowing for some groups to never switch to a shortest path tree.
set protocols pim [vrf<vrf-name>] spt-switchover infinity-and-beyond prefix-list <prefix-list>
Optional. Specifies a VRF name. The value is a string. It’s a user-defined VRF set by the command set ip vrf <vrf-name> [description <string>].
Specifies the prefix-list name. The value is a string which has been set by comannd set routing prefix-list.
When the LHR receives the first multicast packet, it sends a PIM (S,G) join towards the FHR to efficiently forward traffic through the network. This builds the shortest path tree (SPT), or the tree that is the shortest path to the source. When the traffic arrives over the SPT, a PIM (S,G) RPT prune is
sent up the shared tree towards the RP. This removes multicast traffic from the shared tree; multicast data is only sent over the SPT.
You can configure SPT switchover on a per-group basis, allowing for some groups to never switch to a shortest path tree; this is also called SPT infinity. The LHR now sends both (*,G) joins and (S,G) RPT prune messages towards the RP.
To configure a group to never follow the SPT, create the necessary prefix lists, then configure SPT switchover for the prefix-list.
- The following example is to configure a group to never follow the SPT, create the necessary prefixlists, then configure SPT switchover for the spt-range prefix-list: