Storm Control

• Catalyst switches need rate-limiting traffic at layer-2
• To do this uses the storm-control commands.
• Storm control configured to set min & max port traffic (unicast, multicast & broadcast).
• Each rate limit can be configured on a per-port basis.
• Storm control can be configured on each type of traffic based on
• Either packet rate or a percentage of the interface bandwidth.
• We can also specify rising & falling thresholds for each traffic type.
• If we don't specify falling threshold or if the falling threshold is the same as the rising threshold
• the switch port forward all traffic up to the configured limit 
• and will not wait for the specified falling threshold before forwarding it again.
• When any of the configured threshold is passed, the switch can take 3 additional actions (also on port basis)
• 1st & default is the switch can rate-limit by discarding excess traffic according to the configured commands & take no further action.
• The other 2 actions include performing the rate-limiting function & either shutting down the port or sending an SNMP trap.
• Commands
• interface f0/0
• storm-control broadcast level pps 100 50
• limit broadcast traffic to 100packets per seconds
• when traffic drops back to 50 pack/sec, begin forwarding traffic again.
• storm-control multicast level 0.50 0.40
• limit multicast traffic to 0.5 percent of the 100Mbps interface rate
• when traffic drops back to 400kbps, begin forwarding again
• storm-control action trap
• any of above conditions occure & results in rate-limiting, send an SNMP trap.
• show storm-control f0/0 {unicast | multicast \ broadcast }
• Limitation:
• it supports only physical ports
• storm control configure on etherchannel interface, but it has no effect.
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