User guide

PIM Overview Configuring PIM
page 7-16 OmniSwitch AOS Release 7 Advanced Routing Configuration Guide March 2015
SPT Switchover
The last hop Designated Router (DR) initiates the switchover to a true Shortest Path Tree (SPT) once the
DR receives the first multicast data packet. This method does not use any preconfigured thresholds, such
as RP threshold (as described above). Instead, the switchover is initiated automatically, as long as the SPT
status is enabled on the switch.
Important. SPT status must be enabled for SPT switchover to occur. If the SPT status is disabled, the SPT
switchover will not occur. The SPT status is configured via the ip pim spt admin-state command. To
view the current SPT status, use the show ip pim sparse command.
Upon receiving the first multicast data packet, the last hop DR issues a (S, G) source-specific Join message
toward the source.
Sender
Receiver
RP
DR
DR
SPT switchover is enabled at the
last hop DR; the switchover is
initiated upon receiving the first
multicast data packet.
Legend
Source-Specific Join
Multicast Traffic
Source-Specific Join