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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 73 Configuring NetFlow-lite
Configuring NetFlow Packet Sampling
Interface GigabitEthernet1/3:
Netflow-lite Monitor-1:
Active: TRUE
Sampler: sampler1
Exporter: exporter1
Average Packet Size: 0
Statistics:
Packets exported: 0
Packets observed: 0
Packets dropped: 0
Average Packet Size observed: 64
Average Packet Size used: 64
Similarly, you can configure a monitor on a VLAN in VLAN config mode:
Switch# config terminal
Switch(config)# vlan config 2
Switch(config-vlan-config)# netflow-lite monitor 1
Switch(config-netflow-lite-monitor)# average-packet-size 128
Switch(config-netflow-lite-monitor)# exporter exporter1
Switch(config-netflow-lite-monitor)# sampler sampler1
Switch(config-netflow-lite-monitor)# exit
Switch(config-vlan-config)# exit
Switch(config)#
Switch# show netflow-lite monitor 1 vlan 2
VlanID-2:
Netflow-lite Monitor-1:
Active: TRUE
Sampler: sampler1
Exporter: exporter1
Average Packet Size: 0
Statistics:
Packets exported: 0
Packets observed: 0
Packets dropped: 0
Average Packet Size observed: 64
Average Packet Size used: 64
You can verify your settings with the show policy-map privileged EXEC command.
Usage Guidelines
Only a single packet sampling instance is supported on a monitor. These commands are entered under
the physical port interface mode, port channel interface, or config vlan mode. Monitor is not supported
on other interfaces. If the physical port is a member of a port channel, applying the monitor to the port
has no effect. Instead, the monitor must be applied to the port channel.
When configuring a monitor, the mandatory parameters are sampler and exporter. If no exporter is
associated with a monitor, no samples are exported. If no sampler is specified, no input packet sampling
occurs for that target interface.
The packet sampling mechanism tries to achieve random 1-in-N sampling. The accuracy of the algorithm
is dependent on the size of the packets arriving at a given interface. To tune the relative accuracy of the
algorithm, use the average-packet-size parameter. The whole system supports a maximum of 200
monitors.
The system automatically determines the average packet size at an interface based on observation of
input traffic and uses that value in rate DBL sampling.
Valid range of packet sizes that can be used by the algorithm is 64 - 9216 bytes. A value of 0 is taken to
mean that automatic determination of average packet size is desired.
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