Cisco Nexus 1000V Interface Configuration Guide, Release 4.2(1)SV2(2.1)
Configuring Interface Parameters
Downloads: This chapterpdf (PDF - 1.33MB) The complete bookPDF (PDF - 2.89MB) | The complete bookePub (ePub - 401.0KB) | Feedback

Configuring Interface Parameters

Configuring Interface Parameters

This chapter contains the following sections:

Information About the Basic Interface Parameters

Description

For the vEthernet, Ethernet, and management interfaces, you can configure the description parameter to provide a name for the interface. Using a unique name for each interface allows you to quickly identify the interface when you are looking at a listing of multiple interfaces.

By default, the description for vEthernet interfaces is automatically formatted to contain information about the connected device. The description for a virtual Network Interface Card (vNIC), for example, contains the VM name and network adapter number. You keep this default description or you can override it with a description of your choosing.

Speed and Duplex Modes

The speed and duplex modes are interrelated for each Ethernet and management interface. By default, each interface autonegotiates its speed and duplex modes with the other interface, but you can change these settings. If you change the settings, be sure to use the same speed and duplex mode settings on both interfaces or use autonegotiation for at least one of the interfaces.

Port MTU Size

The maximum transmission unit (MTU) size specifies the maximum frame size that an Ethernet port can process. For transmissions to occur between two ports, you must configure the same MTU size for both ports. A port drops any frames that exceed its MTU size.

By default, the MTU size for each port is 1500 bytes, which is the IEEE 802.3 standard for Ethernet frames. Larger MTU sizes are possible for more efficient processing of data with less overhead. The larger frames, called jumbo frames, can be up to 9000 bytes in size, which is also the fixed system jumbo MTU size in the Cisco Nexus 1000V.

For a Layer 2 port, you can configure an MTU size as the system default of 1500 bytes or the system default jumbo MTU size of 9000 bytes.

Administrative Status

The administrative-status parameter determines whether an interface is up or down. When an interface is administratively down, it is disabled and unable to transmit data. When an interface is administratively up, it is enabled and able to transmit data.

Cisco Discovery Protocol

The Cisco Discovery Protocol (CDP) is a Layer 2 protocol that enables two devices that run CDP to learn about each other. You can use CDP to troubleshoot the network by displaying information about the neighboring devices that are linked through each interface. By default, CDP is enabled.

Port Channel

A port channel is an aggregation of multiple physical interfaces that comprise a logical interface. You can bundle up to eight individual interfaces into a port channel to provide increased bandwidth and redundancy. Port channeling also load balances traffic across these physical interfaces. The port channel stays operational if at least one physical interface within the port channel is operational.

Any configuration changes that you apply to the port channel are applied to each interface member of that port channel.

Guidelines and Limitations

Interface parameters have the following configuration guidelines and limitations:

  • You usually configure Ethernet port speed and duplex mode parameters to auto to allow negotiation of the speed and duplex modes between ports. If you decide to configure the port speed and duplex modes manually for these ports, consider the following:
    • If you set the Ethernet port speed to auto, the device automatically sets the duplex mode to auto.
    • If you enter the no speed, command the device automatically sets both the speed and duplex parameters to auto (the no speed command produces the same results as the speed auto command).
    • If you configure an Ethernet port speed to a value other than auto (for example, 10, 100, or 1000 Mbps), you must configure the connecting port to match. Do not configure the connecting port to negotiate the speed.

    Note


    The device cannot automatically negotiate the Ethernet port speed and duplex modes if the connecting port is configured to a value other than auto.



    Note


    Changing the Ethernet port speed and duplex mode configuration might shut down and reenable the interface.


  • To specify an interface in the CLI, use the following guidelines:
    • For an Ethernet port, use the ethernet slot/port command, where slot is the module slot number and port is the port number.
    • For a vEthernet port, use the vethernet number command, where number is a number from 1 to 1048575.
    • A space is not required between the interface type and the slot/port or interface number. For example, for the Ethernet slot 4, port 5 interface, you can specify either the ethernet 4/5 command or the ethernet4/5 command.
  • Jumbo frames are only supported on the vmxnet3 driver. Attempts to change the MTU appear to succeed but the adapter always drops frames larger than 1500 bytes. For more information, see the VMware KB article http:/​/​kb.vmware.com/​selfservice/​microsites/​search.do?language=en_​US&cmd=displayKC&externalId=1015556.

Configuring the Basic Interface Parameters

Specifying an Interface to Configure

You can specify an interface to configure.

Before You Begin

Log in to the CLI in EXEC mode.

Procedure
     Command or ActionPurpose
    Step 1switch# configure terminal 

    Enters global configuration mode.

     
    Step 2switch(config)# interface interface 

    Enters interface configuration mode for the specified interface.

     
    Step 3switch( config-if)# show interface interface  (Optional)

    Displays the current configuration of interfaces.

    The interface argument is defined as follows:

    • For an Ethernet port, use the ethernet slot/port command, where slot is the module slot number and port is the port number.
    • For the management interface, use the mgmt 0 or mgmt0 command.
    • For a vEthernet port, use the vethernet number command, where number is a number from 1 to 1048575.
     

    This example shows how to specify an interface to configure:

    switch# configure terminal
    switch(config)# interface ethernet 3/1
    switch(config-if)# show interface ethernet 3/1
    switch(config-if)#
    

    Configuring a Description

    You can add a description to an Ethernet, vEthernet, or management interface.

    Before You Begin
    • Log in to the CLI in EXEC mode.
    Procedure
       Command or ActionPurpose
      Step 1switch# configure terminal 

      Enters global configuration mode.

       
      Step 2 switch(config)# interface interface 

      Enters interface configuration mode for the specified interface.

       
      Step 3 switch(config-if)# description string 

      Adds a description of up to 80 alphanumeric characters for the interface and saves it in the running configuration.

       
      Step 4 switch(config-if)# show interface interface  (Optional)

      Displays the interface status, which includes the description.

       
      Step 5switch(config-if)# 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 interface description to Ethernet port 24 on module 3:

      switch# configure terminal 
      switch(config)# interface ethernet 3/24
      switch(config-if)# description Ethernet port 24 on module 3
      switch(config-if)# 
      

      Configuring the Interface Speed and Duplex Modes

      You can configure the interface speed and duplex modes.

      Before You Begin
      • Log in to the CLI in EXEC mode.
      • The interface speed and duplex modes are interrelated, so you should configure both at the same time. To see the speeds and duplex modes that you can configure together for Ethernet and management interfaces, see Speed and Duplex Modes.

        Note


        The interface speed that you specify can affect the duplex mode used for an interface, so you should set the speed before setting the duplex mode. If you set the speed for autonegotiation, the duplex mode is automatically set to be autonegotiated. If you specify a speed of 10 Mbps or 100 Mbps, the port is automatically configured to use half-duplex mode, but you can specify full-duplex mode instead. If you specify a speed of 1000 Mbps (1 Gbps) or faster, full duplex is automatically used.


      • Make sure that the remote port has a speed setting that supports your changes for the local port. If you want to set the local port to use a specific speed, you must set the remote port for the same speed or set the local port to automatically negotiate the speed.
      Procedure
         Command or ActionPurpose
        Step 1switch# configure terminal 

        Enters global configuration mode.

         
        Step 2 switch(config-if)# speed {{10 | 100 | 1000 | {auto [10 100 [1000]]}} | {10000 | auto}} 

        Designates the port speed as follows:

        • For Ethernet ports on the 48-port, 10/100/1000 modules, sets the speed at 10 Mbps, 100 Mbps, or 1000 Mbps, or sets the port to automatically negotiate its speed with the other 10/100/1000 port on the same link.
        • For Ethernet ports on the 32-port, 10-Gigabit Ethernet modules, sets the speed at 10,000 Mbps (10 Gbps) or sets the port to automatically negotiate its speed with the other 10-Gigabit Ethernet port on the link.
        • For management interfaces, sets the speed as 1000 Mbps or sets the port to autonegotiate its speed.
         
        Step 3 switch(config-if)# duplex {full | half | auto} 

        Specifies the duplex mode as full, half, or autonegotiate.

         
        Step 4 switch(config-if)# show interface interface  (Optional)

        (Optional) Displays the interface configuration.

         
        Step 5switch(config-if)# 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 port speed and duplex mode to Ethernet port 1 on module 3:

        switch# configure terminal 
        switch(config)# interface ethernet 3/1
        switch(config-if)# speed 1000
        switch(config-if)# duplex full
        switch(config-if)# show interface ethernet 3/1
        switch(config-if)#
        

        Configuring the MTU Size for an Ethernet Interface

        You can configure the size of the maximum transmission unit (MTU) for a Layer 2 Ethernet interface.

        Before You Begin
        • Log in to the CLI in EXEC mode.
        • Specify an MTU size between 1500 and 9000 bytes for an Ethernet interface.
        • Make sure that the MTU value you set is supported by the VEM physical NIC. See your VMware documentation for more information about supported MTU for physical NICs.
        • Jumbo frames are supported only on the vmxnet3 driver. Attempts to change the MTU appear to succeed but the adapter always drops frames larger than 1500 bytes. For more information, see the VMware KB article http:/​/​kb.vmware.com/​selfservice/​microsites/​search.do?language=en_​US&cmd=displayKC&externalId=1015556
        Procedure
           Command or ActionPurpose
          Step 1switch# configure terminal 

          Enters global configuration mode.

           
          Step 2switch(config)# interface ethernet slot/port 

          Specifies an Ethernet interface to configure, and enters interface configuration mode.

           
          Step 3switch(config-if)# mtu size 

          Specifies an MTU size between 1500 (the default) and 9000 bytes.

           
          Step 4switch( config-if)# show interface ethernet slot/port  (Optional)

          Displays the interface status, which includes the MTU size.

           
          Step 5switch(config-if)# 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 Ethernet interface 3/1 with the default MTU size of 1500 bytes:

          switch# configure terminal
          switch# interface ethernet 3/1
          switch(config-if)# mtu 1500
          switch(config-if)#

          Shutting Down and Activating an Interface

          You can shut down and restart Ethernet or management interfaces.

          Before You Begin
          • Log in to the CLI in EXEC mode.
          • When you shut down an interface, it becomes disabled and the output of monitoring commands show it as being down.
          • To activate an interface that has been shut down, you must restart the device.
          Procedure
             Command or ActionPurpose
            Step 1switch# configure terminal 

            Enters global configuration mode.

             
            Step 2switch(config)# interface interface 

            Specifies an Ethernet interface to configure, and enters interface configuration mode.

             
            Step 3switch(config-if)# shutdown  

            Disables the interface in the running configuration .

             
            Step 4switch( config-if)# show interface interface  (Optional)

            Displays the interface status, which includes the administrative status.

             
            Step 5switch(config-if)# no shutdown  

            Reenables the interface in the running configuration .

             
            Step 6switch( config-if)# show interface interface  (Optional)

            Displays the interface status, which includes the administrative status. The interface argument are defined as follows:

            • For an Ethernet port, use the ethernet slot/port command, where slot is the module slot number and port is the port number.
            • For the management interface, use the mgmt 0 or mgmt0 command.
             
            Step 7switch(config-if)# 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 disable the interface Ethernet port 1 on module 3:

            switch# configure terminal
            switch(config)# interface ethernet 3/1
            switch(config-if)# shutdown
            switch(config-if)# no shutdown
            switch(config-if)# 
            

            Enabling or Disabling CDP

            You can enable or disable the Cisco Discovery Protocol (CDP) for Ethernet and management interfaces.

            Before You Begin
            • Log in to the CLI in EXEC mode.
            • Make sure that CDP is enabled at both ends of the link.
            Procedure
               Command or ActionPurpose
              Step 1switch# configure terminal 

              Enters global configuration mode.

               
              Step 2 switch(config)# interface interface  

              Specifies the interface that you are configuring. The interface argument is defined as follows:

              • For an Ethernet port, use the ethernet slot/port command, where slot is the module slot number and port is the port number.
              • For the management interface, use the mgmt 0 or mgmt0 command.
               
              Step 3 switch(config-if)# [no] cdp enable 

              Enables or disables CDP for the interface in the running configuration. This parameter must be enabled for both interfaces on the same link. As soon as you disable CDP for one of two interfaces, CDP is disabled for the link.

               
              Step 4 switch(config-if)# show interface interface   (Optional)

              Displays the CDP status for the interface in the running configuration. The interface argument is defined as follows:

              • For an Ethernet port, use the ethernet slot/port command, where slot is the module slot number and port is the port number.
              • For the management interface, use the mgmt 0 or mgmt0 command.
               
              Step 5switch(config-if)# 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 CDP for Ethernet port 3/1:

              switch# configure terminal 
              switch(config)# interface ethernet 3/1
              switch(config-if)# cdp enable
              switch(config-if)# 
              

              This example shows how to disable CDP for Ethernet port 3/1:

              n1000v# configure terminal 
              switch(config)# interface ethernet 3/1
              switch(config-if)# no cdp enable
              switch(config-if)# 
              

              Clearing the Interface Counters

              You can clear the Ethernet, vEthernet, and management interface counters.

              Before You Begin

              Log in to the CLI in EXEC mode, configuration mode, or interface configuration mode.

              Procedure
                 Command or ActionPurpose
                Step 1 switch# clear counters interface  

                Clears the counters for the specified interface:

                • ethernet slot/port
                • vethernet number
                • mgmt 0 or mgmt0
                 
                Step 2 switch# show interface interface   (Optional)

                Displays the interface status, which includes the counters, for the specified interface:

                • ethernet slot/port
                • vethernet number
                • mgmt 0 or mgmt0
                 

                This example shows how to clear and reset the counters on Ethernet port 5/5:

                switch# clear counters ethernet 5/5
                switch#

                Verifying the Basic Interface Parameters

                Use one of the following commands to verify the configuration:

                Command Purpose

                show cdp

                Displays the CDP status.

                show interface interface

                Displays the configured states of one or all interfaces.

                show interface brief

                Displays a table of interface states.

                show interface switchport

                Displays the status of Layer 2 ports.

                Feature History for Basic Interface Parameters

                Feature Name

                Releases

                Feature Information

                System jumbo MTU

                4.2(1)SV1(4)

                The system jumbo MTU is fixed at 9000 and cannot be changed.

                Interface MTU

                4.2(1)SV1(4)

                The interface MTU can be configured as a value between 1500 and 9000.

                Basic interface parameters

                4.0(4)SV1(1)

                This feature was introduced.