Traffic statistics from Layer 3 switching can be gathered and sent to an external application for collection and analysis. This is done through the NetFlow Data Export (NDE) facility.
Switches using MLS for Layer 3 switching can send data about expired flows using NDE. This is a natural extension of MLS because the switch uses flow cache data.
Switches using CEF do not inherently use a flow cache, and therefore can't offer statistics through NDE. The Catalyst 6000 PFC2/MSFC2, however, keeps a NetFlow cache independent of the CEF process, strictly for exporting flow data with NDE.
NetFlow data can be sent as several versions: