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:
- NDE version 1 Used in legacy systems; data record includes specific information about the IP traffic flow and the interfaces used to forward it.
- NDE version 5 Adds a sequence number to prevent lost UDP datagrams, and the Border Gateway Protocol (BGP) autonomous system (AS) number for the flow.
- NDE version 7 Used to report flow data from Catalyst switches. Version 7 is not supported on a Catalyst 6000 MSFC.
- NDE version 8 Used to report aggregate flow data from routers, Catalyst 5000 with NFFC, and Catalyst 6000 running MLS or CEF. Version 8 is not supported on a Catalyst 6000 MSFC.
NDE will export flow statistics according to the MLS flow mask that is used by the switch. To see detailed flow records, use a "full" flow mask.
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