Exporting Flows; Inactive - Juniper EX9200 Features Manual

Flow Monitoring Feature Guide for EX9200 Switches
12

Exporting Flows

To direct traffic to a flow collection interface, include the
statement. For more information about flow collection, see
Overview" on page 3.
To configure the cflowd version number, include the
forwarding-options monitoring name output]
Version 8 enables the router software to aggregate the flow information using broader
criteria and reduce cflowd traffic. Version 8 aggregation is performed periodically (every
few seconds) on active flows and when flows are allowed to expire. Because the
aggregation is performed periodically, active timeout events are ignored.
For more information on cflowd properties, see Enabling Flow Aggregation.
Configuring Time Periods When Flow Monitoring Is Active and Inactive
To configure time periods for active flow monitoring and intervals of inactivity, include
the and
flow-active-timeout
forwarding-options monitoring name output]
The
flow-active-timeout
for active flows. If the interval between the time the last packet was received and the
time the flow was last exported exceeds the configured value, the flow is exported.
This timer is needed to provide periodic updates when a flow has a long duration. The
active timeout setting enables the router to retain the start time for the flow as a
constant and send out periodic cflowd reports. This in turn allows the collector to
register the start time and determine that a flow has survived for a duration longer
than the configured active timeout.
NOTE: In active flow monitoring, the cflowd records are exported after a
time period that is a multiple of 60 seconds and greater than or equal to
the configured active timeout value. For example, if the active timeout
value is 90 seconds, the cflowd records are exported at 120-second
intervals. If the active timeout value is 150 seconds, the cflowd records are
exported at 180-second intervals, and so forth.
The flow-inactive-timeout
triggers the flow export. If the interval between the current time and the time that the
last packet for this flow was received exceeds the configured inactive timeout value,
the flow is allowed to expire.
If the flow stops transmitting for longer than the configured inactive timeout value, the
router or switch purges it from the flow table and exports the cflowd record. As a result,
the flow is forgotten as far as the PIC is concerned and if the same 5-tuple appears
again, it is assigned a new start time and considered a new flow.
Both timers are necessary. The active timeout setting is needed to provide information
for flows that constantly transmit packets for a long duration. The inactive timeout setting
export-format
hierarchy level. By default, version 5 is used.
statements at the
flow-inactive-timeout
hierarchy level:
statement specifies the time interval between flow exports
statement specifies the interval of inactivity for a flow that
flow-export-destination
"Active Flow Monitoring
statement at the
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