NetFlow

Overview

NetFlow tracks the number of bytes and packets used by each flow.

There are 3 versions of NetFlow: version 1, 5 and 9.

Version 5 can monitor only ingress.

Version 9 can monitor both ingress and egress.

NetFlow information can be export to an remote host which does the calculation or presentation.

Configuration

R3(config)# ip flow-export version 9
R3(config)# ip flow-export destination 192.168.168.168 5858
R3(config)# int s2/0.302
R3(config-if)# ip flow ingress

R3# show ip flow export
R3# show ip cache flow

Flow Sampling

Monitoring all the flows can result in high bandwidth and CPU utilization. And NetFlow provides a feature that can samples packets rather than monitoring all the packets belongs to a flow.

Configuration

R3(config)# flow-sampler-map FSM_ONEPERCENT
R3(config-sampler)# mode random one-out-of 100
R3(config)# ints2/0.302
R3(config-subif)# flow-sampler FSM_ONEPERCENT

R3# show flow-sampler