To prebuild the SPT for all known (S,G)s joins in the routing table
by triggering PIM joins upstream, even in the absence of any receivers, use the
By default, PIM (S,G) joins are triggered upstream only if the
OIF-list for the (S,G) is not empty. It is useful in certain scenarios—for
example, on the virtual port-channel (vPC) nonforwarding router—to prebuild the
SPTs and maintain the (S,G) states even when the system is not forwarding on
these routes. Prebuilding the SPT ensures faster convergence when a vPC
When you are running virtual port channels (vPCs), enabling this
feature causes both vPC peer switches to join the SPT, even though only one vPC
peer switch actually routes the multicast traffic into the vPC domain. This
behavior results in the multicast traffic passing over two parallel paths from
the source to the vPC switch pair, consuming bandwidth on both paths.
Additionally, when both vPC peer switches join the SPT, one or more upstream
devices in the network may be required to perform additional multicast
replications to deliver the traffic on both parallel paths toward the receivers
in the vPC domain.
This command requires the Enterprise Services license.