Netflow

Netflow is a Cisco developed network protocol that has become an industry standard for monitoring traffic (RFC 3954). Once configured, on a per interface basis, the router builds a NetFlow record for each unique traffic stream. Amongst other details the record includes the number of bytes and packets. The record is output once the flow has finished or at preconfigured time interval via a UDP or STCP flow.

CEF is a prerequisite for Netflow to work. To configure on an interface

Config-if#ip flow {ingress|egress}

Verification

Show ip flow interface
Show ip cache flow

To configure data export

Ip flow-export destination {ip address} {udp port}

Verification

Show ip flow export