Changing The Polling Intervals; Back-Off Mechanism; Sflow On Lag Ports; Enabling Extended Sflow - Dell Force10 Z9000 Configuration Manual

Changing the Polling Intervals

The sflow polling-interval command configures the polling interval for an interface in the maximum number of seconds
between successive samples of counters sent to the collector.
This command changes the global default counter polling (20 seconds) interval. You can configure an interface to use a different
polling interval.
To configure the polling intervals globally (in CONFIGURATION mode) or by interface (in INTERFACE mode), use the following
command.
• 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

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

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sFlow