Configuring Netflow Aging Parameters; Netflow Statistics Collection Configuration Example - Cisco 4500M Software Manual

Chapter 40 Configuring NetFlow Statistics Collection
Monitoring and Maintaining Minimum Masks for Aggregation Schemes
To view the configured value of the minimum mask, use the following commands for each aggregation
scheme, as needed:
Command
Router# show ip cache flow aggregation prefix
Router# show ip cache flow aggregation
destination-prefix
Router# show ip cache flow aggregation
source-prefix

Configuring NetFlow Aging Parameters

You can control when flows are purged from the software flow cache (and, if configured, reported
through NDE) with the configuration aging parameters, Active and Inactive, of the ip flow-cache
timeout command.
Active Aging specifies the period of time in which a flow should be removed from the software flow
cache after the flow is created. Generally, this parameter is used to periodically notify external collection
devices about active flows. This parameter operates independently of existing traffic on the flow. Active
timeout settings tend to be on the order of minutes (default is 30min).
Inactive Aging specifies how long after the last packet is seen a flow is removed. The Inactive parameter
clears the flow cache of "stale" flows thereby preventing new flows from starving (due to lack of
resources). Inactive timeout settings tend to be on the order of seconds (default is 15sec).

NetFlow Statistics Collection Configuration Example

The following example shows how to modify the configuration to enable NetFlow switching. It also
shows how to export the flow statistics for further processing to UDP port 9991 on a workstation with
the IP address of 40.0.0.2. In this example, existing NetFlow Statistics are cleared, thereby ensuring that
the show ip cache flow command displays an accurate summary of the NetFlow switching statistics:
Switch# config t
Enter configuration commands, one per line.
Switch(config)# ip route-cache flow
Switch(config)# ip flow-export destination 40.0.0.2 9991
Switch(config)# ip flow-export version 5
Switch(config)# end
Switch# show ip flow export
Flow export is enabled
Exporting flows to 40.0.0.2 (9991)
Exporting using source IP address 40.0.0.1
Version 5 flow records
2 flows exported in 1 udp datagrams
0 flows failed due to lack of export packet
OL-6696-01
NetFlow Statistics Collection Configuration Example
Purpose
Displays the configured value of the
minimum mask in the prefix aggregation
scheme.
Displays the configured value of the
minimum mask in the destination-prefix
aggregation scheme.
Displays the configured value of the
minimum mask in the source-prefix
aggregation scheme.
End with CNTL/Z.
Software Configuration Guide—Release 12.2(25)EW
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