Eliminating Broadcast Storms - D-Link DES-6300 User Manual

Modular L3 Ethernet Switch User's Guide
smaller the broadcast domain, the less effect a broadcast storm will have. Because VLANs are
implemented at each switch port, they can be quite effective in limiting the scope of broadcast
storms.

Eliminating Broadcast Storms

SNMP agents can be programmed to monitor the number of broadcast packets on switch ports
and act on the data. When the number of broadcast packets on a given port rise past an assigned
threshold, an action can be triggered. When enabled, the usual action is to block the port to
broadcast frames, which discards all broadcast frames arriving at the port from the attached
segment. Not only does this isolate the broadcast domain, but it actually starts removing
broadcast packets from the affected segment. When the number of broadcast packets falls to an
acceptable level (below a falling threshold), the SNMP agent can remove the blocking condition,
returning the port to its normal operational state.
In the DES-6300 switch, the default rising threshold is met when more than 500 broadcast
packets per second are being detected on a specified port. Once the rising threshold is surpassed
for a duration of more than 5 seconds, it will trigger the broadcast storm rising action configured
by the user. The default falling threshold is met if there are less than 250 broadcast packets per
second. It is triggered once the duration is at least 30 seconds. The actions can easily be defined
by using a normal SNMP management program or through the console interface.
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