This article explains why traffic is throttled or discarded when testing a 100-Gigabit Ethernet Module Interface Card (MIC). The host link connecting the Packet Forwarding Engine and Routing Engine is likely to see most of the generated test traffic as a potential DDoS attack. To correct this, the testing setup must be revised, sending the generated test traffic to another device which uses the router with the MIC being tested as a transit interface.

In a scenario where a 100-Gigabit Ethernet MIC is configured and being tested by sending generated test traffic near the line-rate, traffic is being throttle or discarded. This behavior is observed as the interface 'Traffic statistics' shows counts well below the 100 Gigabit interface bandwidth.

For example:

This behavior is usually the result of sending generated test traffic near the line-rate to the router which contains the 100 Gigabit interface as the destination of the traffic. The 100 Gigabit interface bandwidth speeds are for transit traffic passing through the router.

If generated test traffic is sent at near line-rate speeds directly to the router, the host link connecting the Packet Forwarding Engine PFE) and Routing Engine (RE) is likely to see most of the generated test traffic as a potential DDoS attack. The PFE will police and discard the test traffic according to the default behavior of the PFE.

In order to avoid the throughput issue, the testing setup must be revised to send the generated test traffic to another device (e.g., another port on the traffic generator or other 100 Gigabit capable device,) which would use the router with the MIC in testing as a transit interface.

This change will cause the generated test traffic to be forwarded by the Packet Forwarding Engines directly, thus allowing the 100 Gigabit interface in testing to reach the 100 Gigabit throughput.

• Understanding Link-State PDU Throttling for IS-IS Interfaces