Changing the Lan-prune-delay interval


ip pim-sparse propagation-delay [250-2000] 
 vlan [vid] ip pim-sparse propagation-delay [250-2000]

ip pim-sparse override-interval [500-6000] 
 vlan [vid] ip pim-sparse override-interval [500-6000]

A router sharing a VLAN with other multicast routers uses these two values to compute the lan-prune-delay setting (above) for how long to wait for a PIM-SM join after receiving a prune packet from downstream for a particular multicast group.

Multiple routers sharing VLAN

A network may have multiple routers sharing VLAN "X." When an upstream router is forwarding traffic from multicast group "X" to VLAN "Y," if one of the routers on VLAN "Y" does not want this traffic, it issues a prune response to the upstream neighbor. The upstream neighbor then goes into a prune pending state for group "X" on VLAN "Y." (During this period, the upstream neighbor continues to forward the traffic.) During the pending period, another router on VLAN "Y" can send a group "X" join to the upstream neighbor. If this happens, the upstream neighbor drops the prune pending state and continues forwarding the traffic. But if no routers on the VLAN send a join, the upstream router prunes group "X" from VLAN "Y" when the lan-prune-delay timer expires.

(Defaults: propagation-delay = 500 milliseconds; override-interval = 2500 milliseconds)