Handling Broadcast Storms

Handling Broadcast Storms

A broadcast storm is a sudden flood of broadcast messages that clogs the transmission medium, approaching 100 percent of the bandwidth. Broadcast storms cause performance to decline and, in the worst case, computers cannot even access the network. The cause of a broadcast storm is often a malfunctioning network adapter, but a broadcast storm also can be caused when a device on the network attempts to contact another device that either doesn’t exist or for some reason doesn’t respond to the broadcast.

If the broadcast messages are viable packets (or even error-filled but partially legible packets), a network-monitoring or protocol-analysis tool often can determine the source of the storm (see Chapter 12, “Monitoring the Network”). If the broadcast storm is caused by a malfunctioning adapter throwing illegible packets onto the line, and a protocol analyzer can’t find the source, try to isolate the offending PC by removing computers from the network one at a time until the line returns to normal. (For more information, see “Troubleshooting Network Adapter Cards,” earlier in this chapter.)