942 | sFlow
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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 CPU condition is cleared. This is as per sFlow
version 5 draft. Once the back-off changes the sample-rate, users 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. The actual sampling-rate of the interface and the configured sample-rate can be viewed 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.
Extended sFlow
Extended sFlow is supported fully on platform e
Platforms
c and s support extended-switch information processing only.
Extended sFlow packs additional information in the sFlow datagram depending on the type of sampled
packet. The following options can be enabled:
•
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.
Use the command
sflow [extended-switch] [extended-router] [extended-gateway] enable command. By
default packing of any of the extended information in the datagram is disabled.
Use the command
show sflow to confirm that extended information packing is enabled, as shown in
Figure 45-6.
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.
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