Cisco NX-OS

Enable NetFlow:

feature netflow

Define an optional flow exporter by specifying the export format, protocol, destination, and other parameters:

flow exporter exporter-1
  description Flow Collector
  destination a.b.c.d
  source Vlan3
  transport udp 2055
  version 9

Define a flow monitor based on the flow record and flow exporter:

flow monitor netflow-monitor-1
  record netflow-original
  exporter exporter-1

Apply the flow monitor to a source interface:

interface eth0/0
  ip flow monitor netflow-monitor-1 input
  exit

Set timeouts:

flow timeout active 300 (default is 1800 seconds)

Verifying the configuration:

show flow record netflow-original
show flow exporter
show flow monitor netflow-monitor-1

Optionally, create custom record:

flow record custom-netflow-record
  description Custom Netflow Record
  match ipv4 source address
  match ipv4 destination address
  match transport destination-port
  ...
  collect counter bytes
  collect counter packets

Reference:

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/system_management/configuration/guide/sm_nx_os_cg/sm_15netflow.html