Port-Level Traffic Controls
Port-based traffic control features can be used to provide protection at the port level. Catalyst switches offer
Storm Control, Protected Ports, Private Virtual Local Area Network (PVLAN), Port Blocking, and Port Security
features.
Storm Control
A LAN storm typically occurs when hostile packets are flooded on the LAN segment, creating unnecessary and
excessive traffic resulting in network performance degradation. Several factors can cause a storm on a network;
examples include errors in the protocol-stack implementation or a loophole that is exploited in a device
configuration.
The Storm Control feature prevents regular network traffic from being disrupted by a broadcast, multicast, or
unicast packet storm on any of the physical interfaces.
The traffic storm control (also known as a traffic suppression feature) monitors inbound packets over a 1-second
interval and compares it to the configured storm-control suppression level by using one of the following
methods to measure activity:
The percentage of total available bandwidth of the port allocated for the broadcast, multicast, or unicast
traffic
Traffic rate over a 1-second interval in packets per second at which broadcast, multicast, or unicast
packets are received on an interface
With either method, the port blocks traffic when a threshold is reached, filtering out all subsequent packets.
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