The Cisco Catalyst 4000 NetFlow Services Card (WS-F4531) is an optional daughter card for the Catalyst 4000/4500 Supervisor Engine IV or Supervisor Engine V. In Supervisor Engine V-10GE, the NetFlow functionality is embedded in the supervisor engine itself.
It extends the functions of the supervisor engine as it collects NetFlow statistics and enhanced Virtual LAN (VLAN) statistics without any affect on the forwarding performance rates of the supervisor engine.
It is not supported on the Supervisor Engine I, II, or III.
If there is one NetFlow Services Card (WS-F4531) on the active supervisor and it fails, the standby takes over. However, it does not have the NetFlow card installed, and will not be able to support the NetFlow configuration.
When there is a NetFlow card on the slot 1 supervisor and none on the slot2 supervisor, if the 45xx switch is powered up, it randomly picks one of the two supervisors as primary. To avoid this, place the supervisor that has the NetFlow card first to make it active. Then, place the second supervisor, which stays as standby.
As an alternative, issue the redundancy force-switchover command to force a switchover from the active to the standby supervisor engine.