Policy Framework Configuration Guide - Juniper Networks

CHAPTER 13
Introduction to Traffic Sampling,
Forwarding, and Monitoring Overview
The following section describes:
• Traffic Sampling, Forwarding, and Monitoring Overview on page 343
Traffic Sampling, Forwarding, and Monitoring Overview
Traffic sampling allows you to sample IP traffic based on particular input interfaces and
various fields in the packet header. You can also use traffic sampling to monitor any
combination of specific logical interfaces, specific protocols on one or more interfaces,
a range of addresses on a logical interface, or individual IP addresses. Information about
the sampled packets is saved to files on the router's hard disk.
The forwarding policies allow you to configure the per-flow load balancing, port mirroring,
and Domain Name System (DNS) or Trivial File Transfer Protocol (TFTP) forwarding. In
Junos OS Release 9.0 and later, you can configure per-prefix load balancing. This feature
enables the router to elect the next hop independent of the route chosen by other routers.
The result is a better utilization of available links.
Traffic sampling and forwarding are supported only on routers equipped with an Internet
Processor II application-specific integrated circuit (ASIC). To determine whether a routing
platform has an Internet Processor II ASIC, use the show chassis hardware command.
Traffic sampling is not meant to capture all packets received by a router. We do not
recommend excessive sampling (a rate greater than 1/1000 packets), because it can
increase the load on your processor. If you need to set a higher sampling rate to diagnose
a particular problem or type of traffic received, we recommend that you revert to a lower
sampling rate after you discover the problem or troublesome traffic.
Copyright © 2010, Juniper Networks, Inc.
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