Policy Framework Configuration Guide - Juniper Networks

Junos 10.4 Policy Framework Configuration Guide
NOTE: This statement is not valid for port mirroring.
Specify the maximum length of the sampled packet by using the maximum-packet-length
bytes statement. For bytes, specify a value from 0 through 9192.
Specify the sampling rate by setting the values for rate and run-length (see Figure 14 on
page 348).
Figure 14: Configure Sampling Rate
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The forwarding plane provides support for random sampling that can be configured
through the rate or run-length statement. The rate statement sets the ratio of the number
of packets to be sampled on an average. For example, if you configure a rate of 10, on
average every tenth packet (1 packet out of 10) is sampled.
The run-length statement specifies the number of matching packets to sample following
the initial one-packet trigger event. Configuring a run length greater than 0 allows you
to sample packets following those already being sampled.
NOTE: The run-length and maximum-packet-length configuration statements
are not supported on MX80 routers.
You can also send the sampled packets to a specified host using the cflowd version 5
and 8 formats or the version 9 format as defined in RFC 3954. For more information, see
“Configuring Flow Aggregation (cflowd)” on page 351 and “Configuring Active Flow
Monitoring Using Version 9” on page 354.
The Junos OS does not sample packets originating from the router. If you configure a
sampling filter and apply it to the output side of an interface, then only the transit packets
going through that interface are sampled. Packets that are sent from the Routing Engine
to the Packet Forwarding Engine are not sampled.
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