sflow sample

The value range for the sampling rate is from 256 through 16777215

The sampling rate is a fraction in the form 1/N, meaning that, on average, one out of every N packets is sampled. The sflow sample command specifies N, the denominator of the fraction. Thus a higher number for the denominator means a lower sampling rate since fewer packets are sampled. Likewise, a lower number for the denominator means a higher sampling rate because more packets are sampled. For example, if you change the denominator from 4096 to 2048, the sampling rate increases because four times as many packets are sampled.

On RUCKUS ICX 7750, ICX 7450, ICX 7250, ICX 7650, ICX 7850, and ICX 7550 the CPU-bound sFlow sample packets are rate-limited to 50 samples per second to avoid high CPU utilization.

The sampling rate must be set depending on input traffic rate. If the input traffic rate is more on the interface, the sampling rate must be configured to a higher value to keep the number of sample packets within the CPU rate limit. Else, the excess sample packets are dropped by the CPU.

The following examples show the ideal sample rate configurations for various input rates that keep the sample packets within the CPU rate limit.

• If the input traffic rate is 200,000 packets/sec, the interface sample rate must be set to 4096. (200000/4096 = less than 50 samples)
• If the input traffic rate is 400,000 packets/sec, the interface sample rate must be set to 8192. (400000/8192 = less than 50 samples)

You cannot change a module's sampling rate directly. You can change a module's sampling rate only by changing the sampling rate of a port on that module.

You can configure an individual port to use a different sampling rate than the global default sampling rate. This is useful when ports have different bandwidths.

You can configure individual LAG ports to use a different sampling rate than the global default sampling rate. For a keep-alive LAG, sFlow can be enabled only at the interface level and not at the LAG level.

When configuring the sample rate, if you configure the value as 1000, the software rounds the value to the next higher odd power of 2; so the actual rate is 2^{^}11 (2048), and 1 in 2048 packets are sampled by the hardware.

The no form of the command resets the sampling rate to the default value.