Heavy memory usage
Heavy use of PIM (many S/G flows over many VLANs), combined with other memory-intensive features, can oversubscribe memory resources and impact overall performance. If available memory is exceeded, the switch drops any new multicast flows and generates appropriate Event Log messages. Corrective actions can include:
Reducing the number of VLANs on the switches by moving some VLANs to another device.
Freeing up system resources by disabling another, non-PIM feature.
Moving some hosts to another device.
For more information, see Operating notes and Messages related to PIM operation.