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Network Management and Monitoring Guide
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Example: Configure sFlow Technology to Monitor Network Traffic

date_range 28-Nov-23

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

Requirements

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

Topology

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

Configuration

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:

content_copy zoom_out_map
[edit protocols]
set sflow collector 10.204.32.46 udp-port 5600                 
set sflow interfaces ge-0/0/0
set sflow polling-interval 20
set sflow sample-rate egress 1000
                                     

Procedure

Step-by-Step Procedure

To configure sFlow technology:

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

    content_copy zoom_out_map
    [edit protocols]
    user@switch# set sflow collector 10.204.32.46 udp-port 5600
    Note:

    You can configure a maximum of 4 collectors.

    The default UDP port is 6343.

  2. Enable sFlow technology on a specific interface:

    content_copy zoom_out_map
    [edit protocols sflow]
    user@switch# set interfaces ge-0/0/0
    Note:

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

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

    content_copy zoom_out_map
    [edit protocols sflow]
    user@switch# set polling-interval 20 
    Note:

    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:

    content_copy zoom_out_map
    [edit protocols sflow]
    user@switch# set sample-rate egress 1000 
    Note:

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

    Note:

    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.
    content_copy zoom_out_map
    [edit protocols sflow]
    user@switch# set sample-size 135 

Results

Check the results of the configuration:

content_copy zoom_out_map
[edit protocols sflow]
user@switch# show
  
polling-interval 20;  
    sample-rate egress 1000;
    collector 10.204.32.46 { 
        udp-port 5600;
    }
interfaces ge-0/0/0.0;
content_copy zoom_out_map
[edit protocols sflow]
user@router# show
polling-interval 20;
source-ip 45.1.1.1;
collector 45.1.1.100;
sample-size 135;

Verification

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

Verifying That sFlow Technology Is Configured Properly

Purpose

Verify that sFlow technology is configured properly.

Action

Use the show sflow command:

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user@switch> show sflow                     
sFlow: Enabled
Sample limit: 300 packets/second
Polling interval: 20 seconds
Sample rate egress: 1:1000: Enabled
Sample rate ingress: 1:2048: Disabled
Agent ID: 10.204.96.222
content_copy zoom_out_map
user@router> show sflow                     
sFlow                   : Enabled
Adaptive fallback       : False
Sample limit            : 2000 packets/second
Sample limit Threshold  : 0 packets/second
Polling interval        : 20 second
Sample rate egress      : 1:2048:Disabled
Sample rate ingress     : 1:2048:Disabled
Agent ID                : 10.204.96.222
Agent ID IPv6           : No valid agent IPv6
Source IP address       : 45.1.1.1
Source IPv6 address     : No valid source IPv6
Sample Size             : 128 Bytes
Note:

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

Meaning

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

Purpose

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

Action

Use the show sflow interface command:

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user@switch> show sflow interface                     
Interface        Status      Sample rate    Adapted sample rate   Polling-interval
            Egress Ingress   Egress Ingress   Egress Ingress
ge-0/0/0.0  Enabled  Disabled  1000    2048    1000     2048            20

Meaning

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

Purpose

Verify the sFlow collector's configuration.

Action

Use the show sflow collector command:

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user@switch> show sflow collector

Collector         Udp-port    No. of samples
 address
10.204.32.46      5600        1000
10.204.32.76      3400        1000
content_copy zoom_out_map
user@router> show sflow collector
Collector                                  Udp-port    Dscp     Forwarding-Class                No. of samples
 address
45.1.1.100                                 6343        0        best-effort                     0

Meaning

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

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