Active Latency Monitoring provides a real-time view of the latency that is incurred by the packets while traveling through the switch on a per port basis. The latency measurement is FIFO measurement. Functionally, as soon as the packet enters the switch, the ASIC adds a timestamp to it. When it is scheduled to go out of the egress port, the egress port calculates the latency for each packet that is going out of that port based on current time and the ingress timestamp on the packet.

Note	Active latency monitoring is currently not available for Cisco Nexus N3548 Series switches. This feature is only supported for Cisco Nexus 3548-X and 3548-XL Series switches.

Each egress port maintains the information in the frame count and the latency register, along with the minimum and maximum latency on that port. The software periodically reads the frame count (default 3 seconds) and the total latency to calculate the average latency per port. Based on per port latency information, the software calculates the average switch latency.

Active Latency Monitoring has the following limitations and guidelines:

• Disabling the latency monitor does not clear the existing latency monitor data.

• Clear the latency monitor data before enabling the latency monitor.

• The latency monitor data is lost when the sampling interval is modified.

• The latency monitor data is not maintained across a switch reload.