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Note: If you want the PE router to stay on the RPT for control traffic, include the spt-threshold statement under the main PIM instance. |
Multicast routers running PIM sparse mode can forward the same stream of multicast packets onto the same LAN through a rendezvous-point tree (RPT) rooted at the RP or a shortest-path tree (SPT) rooted at the source. In some cases, the last-hop router should stay on the shared RPT to the RP and not transition to a direct SPT to the source. For more information about these SPT cutover cases, see SPT Cutover Control.
You configure an SPT threshold policy on the last-hop router to control the transition to a direct SPT. An SPT cutover threshold of infinity applied to a source-group address pair means the last-hop router never transitions to a direct SPT. For all other source-group address pairs, the last-hop router transitions immediately to a direct SPT rooted at the source DR.
To configure the SPT threshold and policy for PIM sparse mode, include the spt-threshold statement:
-
spt-threshold {
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infinity [ spt-threshold-infinity-policies ];
- }
For a list of the hierarchy levels at which you can include this statement, see the statement summary section for this statement.
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Note: If you want the PE router to stay on the RPT for control traffic, include the spt-threshold statement under the main PIM instance. |
The infinity statement must reference a properly configured policy to set the SPT cutover threshold for a particular source-group pair to infinity. The use of values other than infinity for the SPT threshold is not supported. You can configure more than one policy.
Several points are important when configuring the SPT threshold policy, as discussed in the following sections:
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