710
Configuring IP Multicast Routing
Configuring Advanced PIM Features
Troubleshooting PIMv1 and PIMv2 Interoperability Problems
When debugging interoperability problems between PIMv1 and PIMv2, check these in the order shown:
1. Verify RP mapping with the show ip pim rp-hash privileged EXEC command, making sure that all systems agree on
the same RP for the same group.
2. Verify interoperability between different versions of DRs and RPs. Make sure the RPs are interacting with the DRs
properly (by responding with register-stops and forwarding decapsulated data packets from registers).
Configuring Advanced PIM Features
This section includes the following topics:
Delaying the Use of PIM Shortest-Path Tree, page 710 (optional)
Modifying the PIM Router-Query Message Interval, page 712 (optional)
Delaying the Use of PIM Shortest-Path Tree
The change from shared to source tree happens when the first data packet arrives at the last-hop router (Router C in
Figure 89 on page 685 in the Information About PIM Shared Tree and Source Tree, page 684). This change occurs
because the ip pim spt-threshold global configuration command controls that timing.
The shortest-path tree requires more memory than the shared tree but reduces delay. You might want to postpone its
use. Instead of allowing the leaf router to immediately move to the shortest-path tree, you can specify that the traffic
must first reach a threshold.
You can configure when a PIM leaf router should join the shortest-path tree for a specified group. If a source sends at a
rate greater than or equal to the specified kbps rate, the multilayer switch triggers a PIM join message toward the source
to construct a source tree (shortest-path tree). If the traffic rate from the source drops below the threshold value, the
leaf router switches back to the shared tree and sends a prune message toward the source.
You can specify to which groups the shortest-path tree threshold applies by using a group list (a standard access list). If
a value of 0 is specified or if the group list is not used, the threshold applies to all groups.
This procedure is optional.
BEFORE YOU BEGIN
Review the Information About PIM Shared Tree and Source Tree, page 684.
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