Back-Off Mechanism; Sflow On Lag Ports; Enabling Extended Sflow - Dell S4820T Configuration Manual

– 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

The S-Series platforms support extended-switch information processing only.
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
Egress Management Interface sFlow services are disabled
Global default sampling rate: 32768
Global default counter polling interval: 20
Global default extended maximum header size: 128 bytes
Global extended information enabled: none
sFlow
881