Configuration Considerations

The sampling rate is a fraction in the form 1/N, meaning that, on average, one out of every N packets will be sampled. The sFlow sample command at the global level or port level 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 512 to 128, the sampling rate increases because four times as many packets will be sampled.

The software rounds the value you enter to the next higher odd power of 2. This value becomes the actual default sampling rate and is one of the following.

• 2
• 8
• 32
• 128
• 512
• 2048
• 8192
• 32768
• 131072
• 524288
• 2097152
• 8388608
• 33554432
• 134217728
• 536870912
• 2147483648

For example, if the configured sampling rate is 1000, then the actual rate is 2048 and 1 in 2048 packets are sampled by the hardware.