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• Change the global default counter polling interval.
CONFIGURATION mode or INTERFACE mode
sflow polling-interval interval value
– interval value: in seconds.
The range is from 15 to 86400 seconds.
The default is 20 seconds.
Back-Off Mechanism
If the sampling rate for an interface is set to a very low value, the CPU can get overloaded with flow
samples under high-traffic conditions.
In such a scenario, a binary back-off mechanism gets triggered, which doubles the sampling-rate (halves
the number of samples per second) for all interfaces. The backoff mechanism continues to double the
sampling-rate until the CPU condition is cleared. This is as per sFlow version 5 draft. After the back-off
changes the sample-rate, you must manually change the sampling rate to the desired value.
As a result of back-off, the actual sampling-rate of an interface may differ from its configured sampling
rate. You can view the actual sampling-rate of the interface and the configured sample-rate by using the
show sflow command.
sFlow on LAG ports
When a physical port becomes a member of a LAG, it inherits the sFlow configuration from the LAG port.
Enabling Extended sFlow
Extended sFlow packs additional information in the sFlow datagram depending on the type of sampled
packet.
You can enable the following options:
• extended-switch — 802.1Q VLAN ID and 802.1p priority information.
• extended-router — Next-hop and source and destination mask length.
• extended-gateway — Source and destination AS number and the BGP next-hop.
NOTE: The entire AS path is not included. BGP community-list and local preference information are
not included. These fields are assigned default values and are not interpreted by the collector.
• Enable extended sFlow.
sflow [extended-switch] [extended-router] [extended-gateway] enable
By default packing of any of the extended information in the datagram is disabled.
• Confirm that extended information packing is enabled.
show sflow
Examples of Verifying Extended sFlow
The bold line shows that extended sFlow settings are enabled on all three types.
Dell#show sflow
sFlow services are enabled
sFlow
841