The following figure shows the broadcast traffic patterns on an Ethernet interface during a specified time
interval. In this example, traffic storm control occurs between times T1 and T2 and between T4 and T5. During
those intervals, the amount of broadcast traffic exceeded the configured threshold.
Figure 18: Broadcast Suppression
The traffic storm control threshold numbers and the time interval allow the traffic storm control algorithm to
work with different levels of packet granularity. For example, a higher threshold allows more packets to pass
through.
Traffic storm control is implemented in the hardware. The traffic storm control circuitry monitors packets
that pass from an Ethernet interface to the switching bus. Using the Individual/Group bit in the packet destination
address, the circuitry determines if the packet is unicast or broadcast, tracks the current count of packets within
the 10-microsecond interval, and filters out subsequent packets when a threshold is reached.
Traffic storm control uses a bandwidth-based method to measure traffic. You set the percentage of total
available bandwidth that the controlled traffic can use. Because packets do not arrive at uniform intervals, the
10-microsecond interval can affect the operation of traffic storm control.
The following are examples of how traffic storm control operation is affected:
•
If you enable broadcast traffic storm control, and broadcast traffic exceeds the level within the
10-microsecond interval, traffic storm control drops all exceeding broadcast traffic until the end of the
interval.
•
If you enable multicast traffic storm control, and the multicast traffic exceeds the level within the
10-microsecond interval, traffic storm control drops all exceeding multicast traffic until the end of the
interval.
•
If you enable broadcast and multicast traffic storm control, and broadcast traffic exceeds the level within
the 10-microsecond interval, traffic storm control drops all exceeding broadcast traffic until the end of
the interval.
•
If you enable broadcast and multicast traffic storm control, and multicast traffic exceeds the level within
the 10-microsecond interval, traffic storm control drops all exceeding multicast traffic until the end of
the interval.
By default, Cisco NX-OS takes no corrective action when traffic exceeds the configured level.
Cisco Nexus 6000 Series NX-OS Layer 2 Switching Configuration Guide, Release 7.x
142
Configuring Traffic Storm Control
Information About Traffic Storm Control
