Reference Guide

Figure 123. sFlow Traffic Monitoring System
Implementation Information
Dell Networking sFlow is designed so that the hardware sampling rate is per line card port-pipe and is
decided based on all the ports in that port-pipe.
If you do not enable sFlow on any port specifically, the global sampling rate is downloaded to that port
and is to calculate the port-pipe’s lowest sampling rate. This design supports the possibility that sFlow
might be configured on that port in the future. Back-off is triggered based on the port-pipe’s hardware
sampling rate.
For example, if port 1 in the port-pipe has sFlow configured with a 16384 sampling rate while port 2 in the
port-pipe has sFlow configured but no sampling rate set, Dell Networking OS applies a global sampling
rate of 512 to port 2. The hardware sampling rate on the port-pipe is then set at 512 because that is the
lowest configured rate on the port-pipe. When a high traffic situation occurs, a back-off is triggered and
the hardware sampling rate is backed-off from 512 to 1024. Note that port 1 maintains its sampling rate of
16384; port 1 is unaffected because it maintains its configured sampling rate of 16484.
To avoid the back-off, either increase the global sampling rate or configure all the line card ports with the
desired sampling rate even if some ports have no sFlow configured.
Important Points to Remember
• The Dell Networking OS implementation of the sFlow MIB supports sFlow configuration via snmpset.
• By default, sFlow collection is supported only on data ports. If you want to enable sFlow collection
through management ports, use the management egress-interface-selection and
application sflow-collector commands in Configuration and EIS modes respectively.
• sFlow sampling is done on a per-port basis.
• Dell Networking OS exports all sFlow packets to the collector. A small sampling rate can equate to
many exported packets. A backoff mechanism is automatically applied to reduce this amount. Some
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