Cisco Nexus 3000 Series NX-OS System Management Configuration Guide, Release 5.0(3)U4(1)
Configuring sFLOW
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Configuring sFLOW

This chapter contains the following sections:

Information About sFlow

sFlow allows you to monitor the real-time traffic in data networks that contain switches and routers. It uses the sampling mechanism in the sFlow Agent software on switches and routers for monitoring traffic and to forward the sample data on ingress and egress ports to the central data collector, also called the sFlow Analyzer.

For more information about sFlow, see RFC 3176.

sFlow Agent

The sFlow Agent, which is embedded in the Cisco NX-OS software, periodically samples or polls the interface counters that are associated with a data source of the sampled packets. The data source can be an Ethernet interface, an EtherChannel interface, or a range of Ethernet interfaces. The sFlow Agent queries the Ethernet port manager for the respective EtherChannel membership information and also receives notifications from the Ethernet port manager for membership changes.

When you enable sFlow sampling in the Cisco NX-OS software, based on the sampling rate and the hardware internal random number, the ingress packets and egress packets are sent to the CPU as an sFlow-sampled packet. The sFlow Agent processes the sampled packets and sends an sFlow datagram to the sFlow Analyzer. In addition to the original sampled packet, an sFlow datagram includes the information about the ingress port, egress port, and the original packet length. An sFlow datagram can have multiple sFlow samples.

Licensing Requirements

This feature does not require a license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

Prerequisites

You must enable the sFlow feature using the feature sflow command to configure sFlow.

Guidelines and Limitations for sFlow

When you plan your sFlow configuration, consider the following:

  • When you enable sFlow for an interface, it is enabled for both ingress and egress. You cannot enable sFlow for only ingress or only egress.
  • sFlow egress sampling for multicast, broadcast, or unknown unicast packets is not supported.
  • You should configure the sampling rate based on the sFlow configuration and traffic in the system.
  • Cisco Nexus 3000 Series supports only one sFlow collector.

Default Settings for sFlow

Table 1 Default sFlow Parameters
Parameters Default
sFlow sampling-rate 4096
sFlow sampling-size 128
sFlow max datagram-size 1400
sFlow collector-port 6343
sFlow counter-poll-interval 20

Configuring sFLow

Enabling the sFlow Feature

You must enable the sFlow feature before you can configure sFlow on the switch.

Procedure
     Command or ActionPurpose
    Step 1switch# configure terminal 

    Enters global configuration mode.

     
    Step 2[no] feature sflow
     

    Enables the sFlow feature.

     
    Step 3show feature
          		(Optional)

    Displays enabled and disabled features.

     
    Step 4switch(config)# copy running-config startup-config  (Optional)

    Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

     

    This example shows how to enable the sFlow feature:

    switch# configure terminal
switch(config)# feature sflow
switch(config)# copy running-config startup-config

    Configuring the Sampling Rate

    Before You Begin

    Ensure that you have enabled the sFlow feature.

    Procedure
       Command or ActionPurpose
      Step 1switch# configure terminal 

      Enters global configuration mode.

       
      Step 2[no] sflow sampling-rate sampling-rate
       

      Configures the sFlow sampling rate for packets.

      The sampling-rate can be an integer between 4096-1000000000. The default value is 4096.

      Note   

      A sampling-rate of 0 disables sampling.

       
      Step 3show sflow
              		(Optional)

      Displays sFlow information.

       
      Step 4switch(config)# copy running-config startup-config  (Optional)

      Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

       

      This example shows how to set the sampling rate to 50,000:

      switch# configure terminal
switch(config)# sflow sampling-rate 50000
switch(config)# copy running-config startup-config

      Configuring the Maximum Sampled Size

      You can configure the maximum number of bytes that should be copied from a sampled packet.

      Before You Begin

      Ensure that you have enabled the sFlow feature.

      Procedure
         Command or ActionPurpose
        Step 1switch# configure terminal 

        Enters global configuration mode.

         
        Step 2[no] sflow max-sampled-size sampling-size
         

        Configures the sFlow maximum sampling size packets.

        The range for the sampling-size is from 64 to 256 bytes. The default value is 128.

         
        Step 3show sflow
                  		(Optional)

        Displays sFlow information.

         
        Step 4switch(config)# copy running-config startup-config  (Optional)

        Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

         

        This example shows how to configure the maximum sampling size for the sFlow Agent:

        switch# configure terminal
switch(config)# sflow max-sampled-size 200
switch(config)# copy running-config startup-config

        Configuring the Counter Poll Interval

        You can configure the maximum number of seconds between successive samples of the counters that are associated with the data source. A sampling interval of 0 disables counter sampling.

        Before You Begin

        Ensure that you have enabled the sFlow feature.

        Procedure
           Command or ActionPurpose
          Step 1switch# configure terminal 

          Enters global configuration mode.

           
          Step 2[no] sflow counter-poll-interval poll-interval
           

          Configures the sFlow poll interval for an interface. The range for the poll-interval is from 0 to 2147483647 seconds. The default value is 20.

           
          Step 3show sflow
                      		(Optional)

          Displays sFlow information.

           
          Step 4switch(config)# copy running-config startup-config  (Optional)

          Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

           

          This example shows how to configure the sFlow poll interval for an interface:

          switch# configure terminal
switch(config)# sflow counter-poll-interval 100
switch(config)# copy running-config startup-config

          Configuring the Maximum Datagram Size

          You can configure the maximum number of data bytes that can be sent in a single sample datagram.

          Before You Begin

          Ensure that you have enabled the sFlow feature.

          Procedure
             Command or ActionPurpose
            Step 1switch# configure terminal 

            Enters global configuration mode.

             
            Step 2[no] sflow max-datagram-size datagram-size
             

            Configures the sFlow maximum datagram size.

            The range for the datagram-size is from 200 to 9000 bytes. The default value is 1400.

             
            Step 3show sflow
                          		(Optional)

            Displays sFlow information.

             
            Step 4switch(config)# copy running-config startup-config  (Optional)

            Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

             

            This example shows how to configure the sFlow maximum datagram size:

            switch# configure terminal
switch(config)# sflow max-datagram-size 2000
switch(config)# copy running-config startup-config
[########################################] 100%

            Configuring the sFlow Analyzer Address

            Before You Begin

            Ensure that you have enabled the sFlow feature.

            Procedure
               Command or ActionPurpose
              Step 1switch# configure terminal 

              Enters global configuration mode.

               
              Step 2[no] sflow collector-ip IP-address vrf-instance
               

              Configures the IPv4 address for the sFlow Analyzer.

              vrf-instance can be one of the following:

              • A user-defined VRF name. You can specify a maximum of 32 alphanumeric characters.
              • vrf management. You must use this option if the sFlow data collector is on the network connected to the management port.
              • vrf default. You must use this option if the sFlow data collector is on the network connected to the front panel ports.
               
              Step 3show sflow
                              		(Optional)

              Displays sFlow information.

               
              Step 4switch(config)# copy running-config startup-config  (Optional)

              Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

               

              This example shows how to configure the IPv4 address of the sFlow data collector that is connected to the management port:

              switch# configure terminal
switch(config)# sflow collector-ip 192.0.2.5 vrf management
switch(config)# copy running-config startup-config

              Configuring the sFlow Analyzer Port

              You can configure the destination port for sFlow datagrams.

              Before You Begin

              Ensure that you have enabled the sFlow feature.

              Procedure
                 Command or ActionPurpose
                Step 1switch# configure terminal 

                Enters global configuration mode.

                 
                Step 2[no] sflow collector-port collector-port
                 

                Configures the UDP port of the sFlow Analyzer.

                The range for the collector-port is from 0 to 65535. The default value is 6343.

                 
                Step 3show sflow
                                  		(Optional)

                Displays sFlow information.

                 
                Step 4switch(config)# copy running-config startup-config  (Optional)

                Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

                 

                This example shows how to configure the destination port for sFlow datagrams:

                switch# configure terminal
switch(config)# sflow collector-port 7000
switch(config)# copy running-config startup-config
[########################################] 100%
switch(config)#

                Configuring the sFlow Agent Address

                Before You Begin

                Ensure that you have enabled the sFlow feature.

                Procedure
                   Command or ActionPurpose
                  Step 1switch# configure terminal 

                  Enters global configuration mode.

                   
                  Step 2[no] sflow agent-ip ip-address
                   

                  Configures the IPv4 address of the sFlow Agent.

                  The default ip-address is 0.0.0.0, which means that all sampling is disabled on the switch. You must specify a valid IP address to enable sFlow functionality.

                   
                  Step 3show sflow
                                      		(Optional)

                  Displays sFlow information.

                   
                  Step 4switch(config)# copy running-config startup-config  (Optional)

                  Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

                   

                  This example shows how to configure the IPv4 address of the sFlow Agent:

                  switch# configure terminal
switch(config)# sflow agent-ip 192.0.2.3
switch(config)# copy running-config startup-config

                  Configuring the sFlow Sampling Data Source

                  The sFlow sampling data source can be an Ethernet port, a range of Ethernet ports, or a port channel.

                  Before You Begin
                  • Ensure that you have enabled the sFlow feature.
                  • If you want to use a port channel as the data source, ensure that you have already configured the port channel and you know the port channel number.
                  Procedure
                     Command or ActionPurpose
                    Step 1switch# configure terminal 

                    Enters global configuration mode.

                     
                    Step 2switch(config)# [no] sflow data-source interface [ethernet slot/port[-port] |port-channel channel-number] 

                    Configures the sFlow sampling data source.

                    For an Ethernet data source, slot is the slot number and port can be either a single port number or a range of ports designated as port-port.

                     
                    Step 3switch(config)# show sflow  (Optional)

                    Displays sFlow information.

                     
                    Step 4switch(config)# copy running-config startup-config  (Optional)

                    Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

                     

                    This example shows how to configure Ethernet ports 5 through 12 for the sFlow sampler:

                    switch# configure terminal
switch(config)# sflow data-source interface ethernet 1/5-12
switch(config)# copy running-config startup-config
[########################################] 100%
switch(config)#

                    This example shows how to configure port channel 100 for the sFlow sampler:

                    switch# configure terminal
switch(config)# sflow data-source interface port-channel 100
switch(config)# copy running-config startup-config
[########################################] 100%
switch(config)#

                    sFLOW Show Commands

                    To display the sFlow configuration information, perform one of the following tasks:

                    Command Purpose

                    show sflow

                    Displays the sFlow global configuration.

                    show sflow statistics

                    Displays the sFlow statistics.

                    clear sflow statistics

                    Clears the sFlow statistics.

                    show running-config sflow [all]

                    Displays the current running sFlow configuration.

                    Configuration Examples for sFlow

                    This example shows how to configure sFlow:

                    feature sflow
sflow sampling-rate 5000
sflow max-sampled-size 200
sflow counter-poll-interval 100
sflow max-datagram-size 2000
sflow collector-ip 192.0.2.5 vrf management
sflow collector-port 7000
sflow agent-ip 192.0.2.3
sflow data-source interface ethernet 1/5

                    Additional References for sFlow

                    Table 2 Related Documents for sFlow
                    Related Topic Document Title

                    sFlow CLI commands

                    		 Cisco Nexus 3000 Series NX-OS System Management Command Reference.

                    RFC 3176

                    Defines the sFlow packet format and SNMP MIB.

                    http://www.sflow.org/rfc3176.txt

                    Feature History for sFlow

                    This table includes only the updates for those releases that have resulted in additions or changes to the feature.

                    Feature Name Releases Feature Information

                    sFlow

                    5.0(3)U4(1)

                    This feature was introduced.