Multicast Storm
This event is triggered when the number of multi-cast frames per second is higher than the value configured in the Expert Thresholds setup.
A multicast or data storm is excessive transmission of multicast traffic in a network. This happens when a multicast across a network results in even more responses, and each response results in still more responses, in a snowball effect. If network traffic reaches near 100 percent of the available bandwidth, all network traffic can be blocked.
Multicast storms are often caused by a defective network adapter or defective cabling, where the card or cable floods the network with packets. This can be fixed quickly by disconnecting the computer system from the network and then replacing the Ethernet card, or by checking the network cable for any breaks, kinks, or loosened connectors, and then making repairs as needed.
Possible reasons for the event:
Catastrophic multicast storms may be caused by failure of a device or NIC card. For example, if an NIC card repeats the same ARP request at a rate of several hundred times a second, the requests may be propagated around the network by other devices.
Multicast storms can also be caused by misconfigured NetBIOS/NetBEUI servers or devices.