A storm occurs
when huge amount of broadcast, multicast, or unicast packets flood the LAN,
creating excessive traffic and degrading network performance. Errors in the
protocol-stack implementation or in the network configuration can also cause a
storm. The mechanism to prevent and control such events is known as storm
monitors incoming traffic levels over a 1-second traffic storm control interval
and, during the interval compares the traffic level with the traffic storm
control level configured. The traffic storm control threshold level is a
percentage of the total available bandwidth of the port. Each port has
different storm control levels for broadcast, multicast, and unicast type of
Storm control uses
rising and falling thresholds to block and then restore the forwarding of
broadcast, unicast, or multicast packets.
threshold is the traffic limit after which, that particular traffic is blocked.
threshold is the traffic limit below which, that particular starts forwarding
again, if it was already blocked.
If a particular
type of ingress traffic (unicast, broadcast and multicast) is more than the
rising threshold configured on it, the interface goes to blocked state for that
Storm control prevents traffic on a LAN from being disrupted by a broadcast, multicast, or unicast storm on a port. Storm
control is applicable for physical interfaces and is used to restrict the unicast, broadcast and multicast ingress traffic
on the Layer2 interfaces. The feature is disabled by default on the router.