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Example: Configure sFlow Technology to Monitor Network Traffic

This example describes how to configure and use sFlow technology to monitor network traffic.


You can use QFX Series, EX Series, PTX Series and MX Series devices for the example using the following hardware and software components:

  • One EX Series switch

  • Junos OS Release 9.3 or later for EX Series switches

  • One MX Series router

  • Junos OS Release 18.1 or later for MX Series routers

  • Junos OS Release 11.3 or later

  • One QFX3500 switch


The sFlow agent runs on the switch. It combines interface counters and flow samples and sends them across the network to the sFlow collector. Figure 1 depicts the basic elements of the sFlow system.

Figure 1: sFlow Technology Monitoring SystemsFlow Technology Monitoring System


To configure sFlow technology, perform the following tasks:

CLI Quick Configuration

To quickly configure sFlow technology, copy the following commands and paste them into the switch terminal window:


Step-by-Step Procedure

To configure sFlow technology:

  1. Configure the IP address and UDP port of the collector:


    You can configure a maximum of 4 collectors.

    The default UDP port is 6343.

  2. Enable sFlow technology on a specific interface:


    You cannot enable sFlow technology on a Layer 3 VLAN-tagged interface.

  3. Specify in seconds how often the sFlow agent polls the interface:


    The polling interval can be specified as a global parameter also. Specify 0 if you do not want to poll the interface.

  4. Specify the rate at which egress packets must be sampled:


    You can specify both egress and ingress sampling rates. If you set only the egress sampling rate, the ingress sampling rate will be disabled.


    We recommend that you configure the same sampling rates on all the ports on a line card. If you configure different sampling rates are different, the lowest value is used for all ports. You could still configure different rates on different line cards.

  5. (Optional) Specify the sample size for the raw packet header. The sample size configuration is applicable on PTX10003-80C, PTX10003-160C, PTX10001-36MR, PTX10004, PTX10008 and PTX10016 devices from 23.1R1 Junos OS Evolved release.


Check the results of the configuration:


To confirm that the configuration is correct, perform these tasks:

Verifying That sFlow Technology Is Configured Properly


Verify that sFlow technology is configured properly.


Use the show sflow command:


The sampling limit cannot be configured and is set to 300 packets/second per FPC.


The output shows that sFlow technology is enabled and specifies the values for the sampling limit, polling interval, and the egress sampling rate.

Verifying That sFlow Technology Is Enabled on the Specified Interface


Verify that sFlow technology is enabled on the specified interfaces and display the sampling parameters.


Use the show sflow interface command:


The output indicates that sFlow technology is enabled on the ge-0/0/0.0 interface with an egress sampling rate of 1000, a disabled ingress sampling rate, and a polling interval of 20 seconds.

Verifying the sFlow Collector Configuration


Verify the sFlow collector's configuration.


Use the show sflow collector command:


The output displays the IP address of the collectors and the UDP ports. It also displays the number of samples.