Multicast PIM what triggers an assert forwarder election

In a Multicast topology using Protocol Independent Multicast (PIM), an assert forwarder election is triggered when routers detect duplicate multicast traffic on a network segment.

This occurs when a multicast source, such as R1, sends traffic that is received by multiple routers (e.g., R2 and R3). Both routers will attempt to forward this traffic to the same network segment, leading each to "see" the other's multicast traffic on their Fa0/1 interfaces, prompting an assert election to determine which router should be the forwarder.

If no receivers exist on the segment (e.g., removing R4), there will be no need for traffic requests, eliminating the conditions for a PIM assert election and negating issues related to pruning multicast traffic.

Links

https://networklessons.com/multicast/multicast-pim-assert-explained