Symptom

PIM Assert mechanism doesn't work correctly on LAN segment when last hop routers are running XR. Duplicate mcast traffic is seen every 3 mins for a few ms before the Assert timeout happens.

Conditions

This happens only for PIM SSM case, when 2 PES sharing the same LAN segment both are last hop(have igmp joins) for the same S,G. PIM Assert packet from current Winner is accepted by PIM process on current Loser but it didn't cause the assert timer to be reset on Loser so that Loser starts forwarding mcast into LAN for a brief moment. Original Winner detects it and sends another Assert, which is processed completely and duplicate mcast on LAN disappears. This situation repeats every 3 minutes.

Workaround

Remove the static join group configs on both routers and reconfigure. That will be put the routers in steady state and no asserts will be generated.

Further Problem Description