Configuring Basic Interface Parameters

This chapter describes how to configure the basic interface parameters on Cisco NX-OS devices.

About the Basic Interface Parameters

Description

For the Ethernet and management interfaces, you can configure the description parameter to provide a recognizable 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.

For information about setting the description parameter for port-channel interfaces, see the “Configuring a Port-Channel Description” section. For information about configuring this parameter for other interfaces, see the “Configuring the Description” section.

Beacon

The beacon mode allows you to identify a physical port by flashing its link state LED with a green light. By default, this mode is disabled. To identify the physical port for an interface, you can activate the beacon parameter for the interface.

For information about configuring the beacon parameter, see the “Configuring the Beacon Mode” section.

Error Disabled

A port is in the error-disabled (err-disabled) state when the port is enabled administratively (using the no shutdown command) but disabled at runtime by any process. For example, if UDLD detects a unidirectional link, the port is shut down at runtime. However, because the port is administratively enabled, the port status displays as err-disable. Once a port goes into the err-disable state, you must manually reenable it or you can configure a timeout value that provides an automatic recovery. By default, the automatic recovery is not configured, and by default, the err-disable detection is enabled for all causes.

When an interface is in the err-disabled state, use the errdisable detect cause command to find information about the error.

You can configure the automatic error-disabled recovery timeout for a particular error-disabled cause and configure the recovery period.

The errdisable recovery cause command provides an automatic recovery after 300 seconds.

You can use the errdisable recovery interval command to change the recovery period within a range of 30 to 65535 seconds. You can also configure the recovery timeout for a particular err-disable cause.

If you do not enable the error-disabled recovery for the cause, the interface stays in the error-disabled state until you enter the shutdown and no shutdown commands. If the recovery is enabled for a cause, the interface is brought out of the error-disabled state and allowed to retry operation once all the causes have timed out. Use the show interface status err-disabled command to display the reason behind the error.

Interface Status Error Policy

Cisco NX-OS policy servers such as Access Control List (ACL) Manager and Quality of Service (QoS) Manager, maintain a policy database. A policy is defined through the command-line interface.

Policies are pushed when you configure a policy on an interface to ensure that policies that are pushed are consistent with the hardware policies. To clear the errors and to allow the policy programming to proceed with the running configuration, enter the no shutdown command. If the policy programming succeeds, the port is allowed to come up. If the policy programming fails, the configuration is inconsistent with the hardware policies and the port is placed in an error-disabled policy state. The error-disabled policy state remains and the information is stored to prevent the same port from being brought up in the future. This process helps to avoid unnecessary disruption to the system.

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, each port has an MTU of 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 9216 bytes in size, which is also the default system jumbo MTU size.

On a Layer 3 interface, you can configure an MTU size between 576 and 9216 bytes.


Note

The global LAN port MTU size applies to the traffic through a Layer 3 Ethernet LAN port that is configured with a nondefault MTU size.

For a Layer 2 port, you can configure an MTU size that is either the system default (1500 bytes) or the system jumbo MTU size (initially 9216 bytes).


Note

If you change the system jumbo MTU size, Layer 2 ports automatically use the system default MTU size (1500 bytes) unless you specify the new system jumbo MTU size for some or all of those ports.

For information about setting the MTU size, see the “Configuring the MTU Size” section.

Bandwidth

Ethernet ports have a fixed bandwidth of 1,000,000 Kb at the physical layer. Layer 3 protocols use a bandwidth value that you can set for calculating their internal metrics. The value that you set is used for informational purposes only by the Layer 3 protocols—it does not change the fixed bandwidth at the physical layer. For example, the Enhanced Interior Gateway Routing Protocol (EIGRP) uses the minimum path bandwidth to determine a routing metric, but the bandwidth at the physical layer remains at 1,000,000 Kb.

For information about configuring the bandwidth parameter for port-channel interfaces, see the “Configuring the Bandwidth and Delay for Informational Purposes” section. For information about configuring the bandwidth parameter for other interfaces, see the “Configuring the Bandwidth” section.

Throughput Delay

Specifying a value for the throughput-delay parameter provides a value used by Layer 3 protocols; it does not change the actual throughput delay of an interface. The Layer 3 protocols can use this value to make operating decisions. For example, the Enhanced Interior Gateway Routing Protocol (EIGRP) can use the delay setting to set a preference for one Ethernet link over another, if other parameters such as link speed are equal. The delay value that you set is in the tens of microseconds.

For information about configuring the bandwidth parameter for port-channel interfaces, see the “Configuring the Bandwidth and Delay for Informational Purposes” section. For information about configuring the throughput-delay parameter for other interfaces, see the “Configuring the Throughput Delay” section.

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.

For information about configuring the administrative status parameter for port-channel interfaces, see the “Shutting Down and Restarting the Port-Channel Interface” section. For information about configuring the administrative-status parameter for other interfaces, see the “Shutting Down and Activating the Interface” section.

Unidirectional Link Detection Parameter

UDLD Overview

The Cisco-proprietary Unidirectional Link Detection (UDLD) protocol allows devices that are connected through fiber-optic or copper (for example, Category 5 cabling) Ethernet cables to monitor the physical configuration of the cables and detect when a unidirectional link exists. When a device detects a unidirectional link, UDLD shuts down the affected LAN port and alerts the user. Unidirectional links can cause a variety of problems.

UDLD performs tasks that autonegotiation cannot perform, such as detecting the identities of neighbors and shutting down misconnected LAN ports. When you enable both autonegotiation and UDLD, Layer 1 detections work to prevent physical and logical unidirectional connections and the malfunctioning of other protocols.

A unidirectional link occurs whenever traffic transmitted by the local device over a link is received by the neighbor but traffic transmitted from the neighbor is not received by the local device. If one of the fiber strands in a pair is disconnected, as long as autonegotiation is active, the link does not stay up. In this case, the logical link is undetermined, and UDLD does not take any action. If both fibers are working normally at Layer 1, UDLD determines whether those fibers are connected correctly and whether traffic is flowing bidirectionally between the correct neighbors. This check cannot be performed by autonegotiation, because autonegotiation operates at Layer 1.

The Cisco Nexus 9000 Series device periodically transmits UDLD frames to neighbor devices on LAN ports with UDLD enabled. If the frames are echoed back within a specific time frame and they lack a specific acknowledgment (echo), the link is flagged as unidirectional and the LAN port is shut down. Devices on both ends of the link must support UDLD in order for the protocol to successfully identify and disable unidirectional links. You can configure the transmission interval for the UDLD frames, either globally or for the specified interfaces.


Note

By default, UDLD is locally disabled on copper LAN ports to avoid sending unnecessary control traffic on this type of media.

The figure shows an example of a unidirectional link condition. Device B successfully receives traffic from device A on the port. However, device A does not receive traffic from device B on the same port. UDLD detects the problem and disables the port.

Figure 1. Unidirectional Link



Default UDLD Configuration

The following table shows the default UDLD configuration.

Table 1 UDLD Default Configuration

Feature

Default Value

UDLD global enable state

Globally disabled

UDLD per-port enable state for fiber-optic media

Enabled on all Ethernet fiber-optic LAN ports

UDLD per-port enable state for twisted-pair (copper) media

Disabled on all Ethernet 10/100 and 1000BASE-TX LAN ports

UDLD aggressive mode

Disabled

UDLD message interval

15 seconds

For information about configuring the UDLD for the device and its port, see the “Configuring the UDLD Mode” section.

UDLD Aggressive and Nonaggressive Modes

UDLD aggressive mode is disabled by default. You can configure UDLD aggressive mode only on point-to-point links between network devices that support UDLD aggressive mode. If UDLD aggressive mode is enabled, when a port on a bidirectional link that has a UDLD neighbor relationship established stops receiving UDLD frame, UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is disabled.

When you enable the UDLD aggressive mode, the following occurs:

One side of a link has a port stuck (both transmission and receive)

One side of a link remains up while the other side of the link is down

In these cases, the UDLD aggressive mode disables one of the ports on the link, which prevents traffic from being discarded.


Note

You enable the UDLD aggressive mode globally to enable that mode on all the fiber ports. You must enable the UDLD aggressive mode on copper ports on specified interfaces.


Tip

When a line card upgrade is being performed during an in-service software upgrade (ISSU) and some of the ports on the line card are members of a Layer 2 port channel and are configured with UDLD aggressive mode, if you shut down one of the remote ports, UDLD puts the corresponding port on the local device into an error-disabled state. This behavior is correct.

To restore service after the ISSU has completed, enter the shutdown command followed by the no shutdown command on the local port.

Port-Channel Parameters

A port channel is an aggregation of physical interfaces that comprise a logical interface. You can bundle up to 32 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.

You can create Layer 3 port channels by bundling compatible Layer 3 interfaces.

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

For information about port channels and for information about configuring port channels, see Chapter 6, “Configuring Port Channels.”

Cisco QSFP+ to SFP+ Adapter Module Support

The Cisco QSFP+ to SFP+ Adapter (QSA) module provides 10G support for the 40G uplink ports that are a part of the Cisco Nexus M12PQ uplink module of the Cisco Nexus 9396PX (N9K-C9396PX) and Cisco Nexus 93128TX (N9K-C93128TX) devices.

A group of six consecutive ports in the M12PQ uplink module must be operating at the same speed (40G or 10G) to use the QSA/QSFP modules.

  • For Cisco Nexus 9396PX devices, 2/1-6 ports form the first port speed group and the remaining 2/7-12 ports form the second port speed group.

  • For Cisco Nexus 93128TX devices, 2/1-6 ports form the first port speed group and the remaining 2/7-8 ports form the second port speed group.

Use the speed-group 10000 command to configure the first port of a port speed group for the QSA. This command specifies the administrator speed preference for the port group. (The default port speed is 40G.)

  • The speed-group 10000 command specifies a speed of 10G.

  • The no speed-group 10000 command specifies a speed of 40G.

After the speed has been configured, the compatible transceiver modules are enabled. The remaining transceiver modules in the port group (incompatible transceiver modules) become error disabled with a reason of "check speed-group config".

QSA Configuration Example

For a Cisco Nexus 9396PX:

  • Using the default configuration on port 2/1, all the QSFPs in port group 2/1-6 are brought up with a speed of 40G. If there are any QSA modules in port group 2/1-6, they are error disabled.

  • Using the speed-group 10000 command to configure port 2/7, all the QSAs in port group 2/7-12 are brought up with a speed of 10G. If there are any QSFP modules in port group 2/7-12, they are error disabled.

Licensing Requirements

The following table shows the licensing requirements for this feature:

Product

License Requirement

Cisco NX-OS

The basic interface parameters require no license. Any feature not included in a license package is bundled with the NX-OS image and is provided at no extra charge to you.

Guidelines and Limitations

Basic interface parameters have the following configuration guidelines and limitations:

  • Fiber-optic Ethernet ports must use Cisco-supported transceivers. To verify that the ports are using Cisco-supported transceivers, use the show interface transceivers command. Interfaces with Cisco-supported transceivers are listed as functional interfaces.

  • A port can be either a Layer 2 or a Layer 3 interface; it cannot be both simultaneously.

    By default, each port is a Layer 3 interface.

    You can change a Layer 3 interface into a Layer 2 interface by using the switchport command. You can change a Layer 2 interface into a Layer 3 interface by using the no switchport command.

  • Flow control using pause frames is not supported.

  • You usually configure Ethernet port speed and duplex mode parameters to auto to allow the system to negotiate the speed and duplex mode between ports. If you decide to configure the port speed and duplex modes manually for these ports, consider the following:

    • Before you configure the speed and duplex mode for an Ethernet or management interface, see the Default Settings section for the combinations of speeds and duplex modes that can be configured at the same time.

    • 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, 1G, 10G, or 40G), you must configure the connecting port to match. Do not configure the connecting port to negotiate the speed.

    • To configure speed, duplex, and automatic flow control for an Ethernet interface, you can use the negotiate auto command. To disable automatic negotiation, use the no negotiate auto command.


    Note

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


    Caution

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

  • For BASE-T copper ports, auto-negotiation is enabled even when fixed speed is configured.

  • The port profile feature is not supported.

Default Settings

The following lists the default settings for the basic interface parameters.

Parameter

Default

Description

Blank

Beacon

Disabled

Bandwidth

Data rate of interface

Throughput delay

100 microseconds

Administrative status

Shutdown

MTU

1500 bytes

UDLD global

Globally disabled

UDLD per-port enable state for fiber-optic media

Enabled on all Ethernet fiber-optic LAN ports

UDLD per-port enable state for copper media

Disabled on all Ethernet 1G, 10G, or 40G LAN ports

UDLD message interval

Disabled

UDLD aggressive mode

Disabled

Error disable

Disabled

Error disable recovery

Disabled

Error disable recovery interval

300 seconds

Buffer-boost

Enabled

Note   

Feature available on N9K-X9564TX and N9K-X9564PX line cards and Cisco Nexus 9300 series devices.

Configuring the Basic Interface Parameters

When you configure an interface, you must specify the interface before you can configure its parameters.

Specifying the Interfaces to Configure

Before You Begin

Before you can configure the parameters for one or more interfaces of the same type, you must specify the type and the identities of the interfaces.

The following table shows the interface types and identities that you should use for specifying the Ethernet and management interfaces.

Table 2 Information Needed to Identify an Interface for Configurations

Interface Type

Identity

Ethernet

I/O module slot numbers and port numbers on the module

Management

0 (for port 0)

The interface range configuration mode allows you to configure multiple interfaces with the same configuration parameters. After you enter the interface range configuration mode, all command parameters you enter are attributed to all interfaces within that range until you exit out of the interface range configuration mode.

You enter a range of interfaces using dashes (-) and commas (,). Dashes separate contiguous interfaces and commas separate noncontiguous interfaces. When you enter noncontiguous interfaces, you must enter the media type for each interface.

This example shows how to configure a contiguous interface range: 

switch(config)# interface ethernet 2/29-30
switch(config-if-range)#

This example shows how to configure a noncontiguous interface range: 

switch(config)# interface ethernet 2/29, ethernet 2/33, ethernet 2/35
switch(config-if-range)#

You can specify subinterfaces in a range only when the subinterfaces are on the same port, for example, 2/29.1-2. But you cannot specify the subinterfaces in a range of ports, for example, you cannot enter 2/29.2-2/30.2. You can specify two of the subinterfaces discretely, for example, you can enter 2/29.2, 2/30.2.

This example shows how to configure a a breakout cable: 

switch(config)# interface ethernet 1/2/1
switch(config-if-range)#
SUMMARY STEPS

    1.    configure terminal

    2.    interface interface


DETAILED STEPS
     Command or ActionPurpose
    Step 1configure terminal


    Example: 
    switch# configure terminal
switch(config)#
     

    Enters global configuration mode.

     
    Step 2interface interface


    Example: 
    switch(config)# interface ethernet 2/1
switch(config-if)#


    Example: 
    switch(config)# interface mgmt0
switch(config-if)#
     

    Specifies the interface that you are configuring. You can specify the interface type and identity. For an Ethernet port, use ethernet slot/port. For the management interface, use mgmt0.

    Examples:

    • The 1st example shows how to specify the slot 2, port 1 Ethernet interface.

    • The 2nd example shows how to specify the management interface.

    Note   

    You do not need to add a space between the interface type and identity (port or slot/port number) For example, for the Ethernet slot 4, port 5 interface, you can specify either “ethernet 4/5” or “ethernet4/5.” The management interface is either “mgmt0” or “mgmt 0.”

    When you are in the interface configuration mode, the commands that you enter configure the interface that you specified for this mode.

     

    Configuring the Description

    You can provide textual interface descriptions for the Ethernet and management interfaces.

    SUMMARY STEPS

      1.    configure terminal

      2.    interface interface

      3.    description text

      4.    show interface interface

      5.    exit

      6.    copy running-config startup-config


    DETAILED STEPS
       Command or ActionPurpose
      Step 1configure terminal


      Example: 
      switch# configure terminal
switch(config)#
       

      Enters global configuration mode.

       
      Step 2interface interface


      Example: 
      switch(config)# interface ethernet 2/1
switch(config-if)#


      Example: 
      switch(config)# interface mgmt0
switch(config-if)#
       

      Specifies the interface that you are configuring. You can specify the interface type and identity. For an Ethernet port, use ethernet slot/port. For the management interface, use mgmt0.

      Examples:

      • The 1st example shows how to specify the slot 2, port 1 Ethernet interface.

      • The 2nd example shows how to specify the management interface.

       
      Step 3description text


      Example: 
      switch(config-if)# description Ethernet port 3 on module 1
switch(config-if)#
       

      Specifies the description for the interface.

       
      Step 4show interface interface


      Example: 
      switch(config)# show interface ethernet 2/1
       

      (Optional) Displays the interface status, which includes the description parameter.

       
      Step 5exit


      Example: 
      switch(config-if)# exit 
switch(config)#
       

      Exits the interface mode.

       
      Step 6copy running-config startup-config


      Example: 
      switch(config)# copy running-config startup-config
       

      (Optional) Copies 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 server1
switch(config-if)#

      The output of the show interface eth command is enhanced as shown in the following example: 

      Switch# show version
Software
BIOS: version 06.26
NXOS: version 6.1(2)I2(1) [build 6.1(2)I2.1]
BIOS compile time: 01/15/2014
NXOS image file is: bootflash:///n9000-dk9.6.1.2.I2.1.bin
NXOS compile time: 2/25/2014 2:00:00 [02/25/2014 10:39:03]

switch# show interface ethernet 6/36
Ethernet6/36 is up
admin state is up, Dedicated Interface
Hardware: 40000 Ethernet, address: 0022.bdf6.bf91 (bia 0022.bdf8.2bf3)
Internet Address is 192.168.100.1/24
MTU 9216 bytes, BW 40000000 Kbit, DLY 10 usec

      Configuring the Beacon Mode

      You can enable the beacon mode for an Ethernet port to flash its LED to confirm its physical location.

      SUMMARY STEPS

        1.    configure terminal

        2.    interface ethernet slot/port

        3.    [no] beacon

        4.    show interface ethernet slot/port

        5.    exit

        6.    copy running-config startup-config


      DETAILED STEPS
         Command or ActionPurpose
        Step 1configure terminal


        Example: 
        switch# configure terminal
switch(config)#
         

        Enters global configuration mode.

         
        Step 2interface ethernet slot/port


        Example: 
        switch(config)# interface ethernet 3/1
switch(config-if)#
         

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

         
        Step 3[no] beacon


        Example: 
        switch(config)# beacon
switch(config-if)#
         

        Enables the beacon mode or disables the beacon mode. The default mode is disabled.

         
        Step 4show interface ethernet slot/port


        Example: 
        switch(config)# show interface ethernet 2/1
switch(config-if)#
         

        (Optional) Displays the interface status, which includes the beacon mode state.

         
        Step 5exit


        Example: 
        switch(config-if)# exit 
switch(config)#
         

        Exits the interface mode.

         
        Step 6copy running-config startup-config


        Example: 
        switch(config)# copy running-config startup-config
         

        (Optional) Copies the running configuration to the startup configuration.

         

        This example shows how to enable the beacon mode for the Ethernet port 3/1: 

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

        This example shows how to disable the beacon mode for the Ethernet port 3/1: 

        switch# configure terminal 
switch(config)# interface ethernet 3/1
switch(config-if)# no beacon
switch(config-if)#
        This example shows how to configure the dedicated mode for Ethernet port 4/17 in the group that includes ports 4/17, 4/19, 4/21, and 4/23: 
        switch# configure terminal 
switch(config)# interface ethernet 4/17, ethernet 4/19, ethernet 4/21, ethernet 4/23
switch(config-if)# shutdown
switch(config-if)# interface ethernet 4/17
switch(config-if)# no shutdown
switch(config-if)#

        Configuring the Error-Disabled State

        You can view the reason an interface moves to the error-disabled state and configure automatic recovery.

        Enabling the Error-Disable Detection

        You can enable error-disable detection in an application. As a result, when a cause is detected on an interface, the interface is placed in an error-disabled state, which is an operational state that is similar to the link-down state.

        SUMMARY STEPS

          1.    configure terminal

          2.    errdisable detect cause (acl-exception | all | link-flap | loopback)

          3.    shutdown

          4.    no shutdown

          5.    show interface status err-disabled

          6.    copy running-config startup-config


        DETAILED STEPS
           Command or ActionPurpose
          Step 1configure terminal


          Example: 
          switch# configure terminal
switch(config)#
           

          Enters global configuration mode.

           
          Step 2errdisable detect cause (acl-exception | all | link-flap | loopback)


          Example: 
          switch(config)# errdisable detect cause all
switch(config-if)#
           

          Specifies a condition under which to place the interface in an error-disabled state. The default is enabled.

           
          Step 3shutdown


          Example: 
          switch(config-if)# shutdown 
switch(config)#
           

          Brings the interface down administratively. To manually recover the interface from the error-disabled state, enter this command first.

           
          Step 4no shutdown


          Example: 
          switch(config-if)# no shutdown 
switch(config)#
           

          Brings the interface up administratively and enables the interface to recover manually from the error-disabled state.

           
          Step 5show interface status err-disabled


          Example: 
          switch(config)# show interface status err-disabled
           

          (Optional) Displays information about error-disabled interfaces.

           
          Step 6copy running-config startup-config


          Example: 
          switch(config)# copy running-config startup-config
           

          (Optional) Copies the running configuration to the startup configuration.

           

          This example shows how to enable the error-disabled detection in all cases: 

          switch(config)# errdisable detect cause all
switch(config)#

          Enabling the Error-Disabled Recovery

          You can specify the application to bring the interface out of the error-disabled state and retry coming up. It retries after 300 seconds, unless you configure the recovery timer (see the errdisable recovery interval command).

          SUMMARY STEPS

            1.    configure terminal

            2.    errdisable recovery cause {all | bpduguard | failed-port-state | link-flap | loopback | miscabling | psecure-violation | security-violation | storm-control | udld | vpc-peerlink}

            3.    show interface status err-disabled

            4.    copy running-config startup-config


          DETAILED STEPS
             Command or ActionPurpose
            Step 1configure terminal


            Example: 
            switch# configure terminal
switch(config)#
             

            Enters global configuration mode.

             
            Step 2errdisable recovery cause {all | bpduguard | failed-port-state | link-flap | loopback | miscabling | psecure-violation | security-violation | storm-control | udld | vpc-peerlink}


            Example: 
            switch(config)# errdisable recovery cause all
switch(config-if)#
             

            Specifies a condition under which the interface automatically recovers from the error-disabled state, and the device retries bringing the interface up. The device waits 300 seconds to retry. The default is disabled.

             
            Step 3show interface status err-disabled


            Example: 
            switch(config)# show interface status err-disabled
switch(config-if)#
             

            (Optional) Displays information about error-disabled interfaces.

             
            Step 4copy running-config startup-config


            Example: 
            switch(config)# copy running-config startup-config
             

            (Optional) Copies the running configuration to the startup configuration.

             

            This example shows how to enable error-disabled recovery under all conditions: 

            switch(config)# errdisable recovery cause all
switch(config)#

            Configuring the Error-Disabled Recovery Interval

            You can configure the error-disabled recovery timer value.

            SUMMARY STEPS

              1.    configure terminal

              2.    errdisable recovery interval interval

              3.    show interface status err-disabled

              4.    copy running-config startup-config


            DETAILED STEPS
               Command or ActionPurpose
              Step 1configure terminal


              Example: 
              switch# configure terminal
switch(config)#
               

              Enters global configuration mode.

               
              Step 2errdisable recovery interval interval


              Example:
              switch(config)# errdisable recovery interval 32
switch(config-if)#
               

              Specifies the interval for the interface to recover from the error-disabled state. The range is from 30 to 65535 seconds, and the default is 300 seconds.

               
              Step 3show interface status err-disabled


              Example:
              switch(config)# show interface status err-disabled
switch(config-if)#
               

              (Optional) Displays information about error-disabled interfaces.

               
              Step 4copy running-config startup-config


              Example:
              switch(config)# copy running-config startup-config
               

              (Optional) Copies the running configuration to the startup configuration.

               

              This example shows how to configure the error-disabled recovery timer to set the interval for recovery to 32 seconds:

              switch(config)# errdisable recovery interval 32
switch(config)#

              Configuring the MTU Size

              You can configure the maximum transmission unit (MTU) size for Layer 2 and Layer 3 Ethernet interfaces. For Layer 3 interfaces, you can configure the MTU to be between 576 and 9216 bytes (even values are required). For Layer 2 interfaces, you can configure the MTU to be either the system default MTU (1500 bytes) or the system jumbo MTU size (which has the default size of 9216 bytes).


              Note

              You can change the system jumbo MTU size, but if you change that value, the Layer 2 interfaces that use that value automatically changes to the new system jumbo MTU value.

              By default, Cisco NX-OS configures Layer 3 parameters. If you want to configure Layer 2 parameters, you need to switch the port mode to Layer 2.

              You can change the port mode by using the switchport command.

              After changing the port mode to Layer 2, you can return to configuring Layer 3 interfaces by changing the port mode again, by using the no switchport command.

              Configuring the Interface MTU Size

              For Layer 3 interfaces, you can configure an MTU size that is between 576 and 9216 bytes.

              For Layer 2 interfaces, you can configure all Layer 2 interfaces to use either the default MTU size (1500 bytes) or the system jumbo MTU size (default size of 9216 bytes).

              If you need to use a different system jumbo MTU size for Layer 2 interfaces, see the “Configuring the System Jumbo MTU Size” section.

              SUMMARY STEPS

                1.    configure terminal

                2.    interface ethernet slot/port

                3.    (switchport | no switchport)

                4.    mtu size

                5.    show interface ethernet slot/port

                6.    exit

                7.    copy running-config startup-config


              DETAILED STEPS
                 Command or ActionPurpose
                Step 1configure terminal


                Example: 
                switch# configure terminal
switch(config)#
                 

                Enters global configuration mode.

                 
                Step 2interface ethernet slot/port


                Example:
                switch(config)# interface ethernet 3/1
switch(config-if)#
                 

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

                 
                Step 3(switchport | no switchport)


                Example:
                switch(config-if)# no switchport
switch(config-if)#
                 

                Specifies to use Layer 3.

                 
                Step 4mtu size


                Example:
                switch(config-if)# mtu 9216
switch(config-if)#
                 

                For a Layer 3 interface, specifies any even number between 576 and 9216.

                 
                Step 5show interface ethernet slot/port


                Example:
                switch(config)# show interface ethernet 2/1
                 

                (Optional) Displays the interface status, which includes the MTU size.

                 
                Step 6exit


                Example:
                switch(config-if)# exit
switch(config)#
                 

                Exits the interface mode.

                 
                Step 7copy running-config startup-config


                Example:
                switch(config)# copy running-config startup-config
                 

                (Optional) Copies the running configuration to the startup configuration.

                 

                This example shows how to configure the Layer 2 Ethernet port 3/1 with the default MTU size (1500):

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

                Configuring the System Jumbo MTU Size

                You can configure the system jumbo MTU size, which can be used to specify the MTU size for Layer 2 interfaces. You can specify an even number between 1500 and 9216. If you do not configure the system jumbo MTU size, it defaults to 9216 bytes.

                SUMMARY STEPS

                  1.    configure terminal

                  2.    system jumbomtu size

                  3.    show running-config all

                  4.    interface type slot/port

                  5.    mtu size

                  6.    exit

                  7.    copy running-config startup-config


                DETAILED STEPS
                   Command or ActionPurpose
                  Step 1configure terminal


                  Example: 
                  switch# configure terminal
switch(config)#
                   

                  Enters global configuration mode.

                   
                  Step 2system jumbomtu size


                  Example: 
                  switch(config)# system jumbomtu 8000
switch(config)#
                   

                  Specifies the system jumbo MTU size. Use an even number between 1500 and 9216.

                  Note   

                  In general accepted practice, a jumbo frame is considered to have an MTU size greater than 9000 bytes.

                   
                  Step 3show running-config all


                  Example: 
                  switch(config)# show running-config all | include jumbomtu
                   

                  (Optional) Displays the current operating configuration, which includes the system jumbo MTU size.

                   
                  Step 4interface type slot/port


                  Example: 
                  switch(config)# interface ethernet 2/1
switch(config-if)#
                   

                  Specifies an interface to configure and enters interface configuration mode.

                   
                  Step 5mtu size


                  Example: 
                  switch(config-if)# mtu 1500
switch(config-if)#
                   

                  For a Layer 2 interface, specifies either the default MTU size (1500) or the system jumbo MTU size that you specified earlier.

                  For a Layer 3 interface, specifies any even size between 576 and 9216.

                   
                  Step 6exit


                  Example: 
                  switch(config-if)# exit
switch(config)#
                   

                  Exits the interface mode.

                   
                  Step 7copy running-config startup-config


                  Example: 
                  switch(config)# copy running-config startup-config
                   

                  (Optional) Copies the running configuration to the startup configuration.

                   

                  This example shows how to configure the system jumbo MTU as 8000 bytes and how to change the MTU specification for an interface that was configured with the previous jumbo MTU size: 

                  switch# configure terminal 
switch(config)# system jumbomtu 8000
switch(config)# show running-config
switch(config)# interface ethernet 2/2
switch(config-if)# switchport
switch(config-if)# mtu 1500
switch(config-if)#

                  Configuring the Bandwidth

                  You can configure the bandwidth for Ethernet interfaces. The physical layer uses an unchangeable bandwidth of 1G, 10G, or 40G, but you can configure a value of 1 to 100,000,000 KB for Level 3 protocols.

                  SUMMARY STEPS

                    1.    configure terminal

                    2.    interface ethernet slot/port

                    3.    bandwidth kbps

                    4.    show interface ethernet slot/port

                    5.    exit

                    6.    copy running-config startup-config


                  DETAILED STEPS
                     Command or ActionPurpose
                    Step 1configure terminal


                    Example: 
                    switch# configure terminal
switch(config)#
                     

                    Enters global configuration mode.

                     
                    Step 2interface ethernet slot/port


                    Example: 
                    switch(config)# interface ethernet 3/1
switch(config-if)#
                     

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

                     
                    Step 3bandwidth kbps


                    Example: 
                    switch(config-if)# bandwidth 1000000
switch(config-if)#
                     

                    Specifies the bandwidth as an informational-only value between 1 and 100,000,000.

                     
                    Step 4show interface ethernet slot/port


                    Example: 
                    switch(config)# show interface ethernet 2/1
                     

                    (Optional) Displays the interface status, which includes the bandwidth value.

                     
                    Step 5exit


                    Example: 
                    switch(config-if)# exit
switch(config)#
                     

                    Exits the interface mode.

                     
                    Step 6copy running-config startup-config


                    Example: 
                    switch(config)# copy running-config startup-config
                     

                    (Optional) Copies the running configuration to the startup configuration.

                     

                    This example shows how to configure an informational value of 1,000,000 Kb for the Ethernet slot 3, port 1 interface bandwidth parameter: 

                    switch# configure terminal 
switch(config)# interface ethernet 3/1
switch(config-if)# bandwidth 1000000
switch(config-if)#

                    Configuring the Throughput Delay

                    You can configure the interface throughput delay for Ethernet interfaces. The actual delay time does not change, but you can set an informational value between 1 and 16777215, where the value represents the number of tens of microseconds.

                    SUMMARY STEPS

                      1.    configure terminal

                      2.    interface ethernet slot/port

                      3.    delay value

                      4.    show interface ethernet slot/port

                      5.    exit

                      6.    copy running-config startup-config


                    DETAILED STEPS
                       Command or ActionPurpose
                      Step 1configure terminal


                      Example: 
                      switch# configure terminal
switch(config)#
                       

                      Enters global configuration mode.

                       
                      Step 2interface ethernet slot/port


                      Example:
                      switch(config)# interface ethernet 3/1
switch(config-if)#
                       

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

                       
                      Step 3delay value


                      Example:
                      switch(config-if)# delay 10000
switch(config-if)#
                       

                      Specifies the delay time in tens of microseconds. You can set an informational value range between 1 and 16777215 tens of microseconds.

                       
                      Step 4show interface ethernet slot/port


                      Example:
                      switch(config)# show interface ethernet 3/1
switch(config-if)#
                       

                      (Optional) Displays the interface status, which includes the throughput-delay time.

                       
                      Step 5exit


                      Example:
                      switch(config-if)# exit
switch(config)#
                       

                      Exits the interface mode.

                       
                      Step 6copy running-config startup-config


                      Example:
                      switch(config)# copy running-config startup-config
                       

                      (Optional) Copies the running configuration to the startup configuration.

                       

                      This example shows how to configure the throughput-delay time so that one interface is preferred over another. A lower delay value is preferred over a higher value. In this example, Ethernet 7/48 is preferred over 7/47. The default delay for 7/48 is less than the configured value on 7/47, which is set for the highest value (16777215):

                      switch# configure terminal 
switch(config)# interface ethernet 7/47
switch(config-if)# delay 16777215
switch(config-if)# ip address 192.168.10.1/24
switch(config-if)# ip router eigrp 10
switch(config-if)# no shutdown
switch(config-if)# exit
switch(config)# interface ethernet 7/48
switch(config-if)# ip address 192.168.11.1/24
switch(config-if)# ip router eigrp 10
switch(config-if)# no shutdown
switch(config-if)#

                      Note

                      You must first ensure the EIGRP feature is enabled by running the feature eigrp command.

                      Shutting Down and Activating the Interface

                      You can shut down and restart Ethernet or management interfaces. When you shut down interfaces, they become disabled and all monitoring displays show them as being down. This information is communicated to other network servers through all dynamic routing protocols. When the interfaces are shut down, the interface is not included in any routing updates. To activate the interface, you must restart the device.

                      SUMMARY STEPS

                        1.    configure terminal

                        2.    interface interface

                        3.    shutdown

                        4.    show interface interface

                        5.    no shutdown

                        6.    show interface interface

                        7.    exit

                        8.    copy running-config startup-config


                      DETAILED STEPS
                         Command or ActionPurpose
                        Step 1configure terminal


                        Example: 
                        switch# configure terminal
switch(config)#
                         

                        Enters global configuration mode.

                         
                        Step 2interface interface


                        Example:
                        switch(config)# interface ethernet 2/1
switch(config-if)#

switch(config)# interface mgmt0
switch(config-if)#
                         

                        Specifies the interface that you are configuring. You can specify the interface type and identity. For an Ethernet port, use ethernet slot/port. For the management interface, use mgmt0.

                        Examples:

                        • The 1st example shows how to specify the slot 2, port 1 Ethernet interface.

                        • The 2nd example shows how to specify the management interface.

                         
                        Step 3shutdown


                        Example:
                        switch(config-if)# shutdown
switch(config-if)#
                         

                        Disables the interface.

                         
                        Step 4show interface interface


                        Example:
                        switch(config-if)# show interface ethernet 2/1
switch(config-if)#
                         

                        (Optional) Displays the interface status, which includes the administrative status.

                         
                        Step 5no shutdown


                        Example:
                        switch(config-if)# no shutdown
switch(config-if)#
                         

                        Reenables the interface.

                         
                        Step 6show interface interface


                        Example:
                        switch(config-if)# show interface ethernet 2/1
switch(config-if)#
                         

                        (Optional) Displays the interface status, which includes the administrative status.

                         
                        Step 7exit


                        Example:
                        switch(config-if)# exit
switch(config)#
                         

                        Exits the interface mode.

                         
                        Step 8copy running-config startup-config


                        Example:
                        switch(config)# copy running-config startup-config
                         

                        (Optional) Copies the running configuration to the startup configuration.

                         

                        This example shows how to change the administrative status for Ethernet port 3/1 from disabled to enabled:

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

                        Configuring the UDLD Mode

                        You can configure normal unidirectional link detection (UDLD) modes for Ethernet interfaces on devices configured to run UDLD.

                        Before you can enable a UDLD mode for an interface, you must make sure that UDLD is already enabled on the device that includes the interface. UDLD must also be enabled on the other linked interface and its device.

                        The following table lists CLI details to enable and disable UDLD on different interfaces

                        Table 3 CLI Details to Enable or Disable UDLD on Different Interfaces

                        Description

                        Fiber port

                        Copper or Nonfiber port

                        Default setting

                        Enabled

                        Disabled

                        Enable UDLD command

                        no udld disable

                        udld enable

                        Disable UDLD command

                        udld disable

                        no udld enable

                        Before You Begin

                        You must enable UDLD for the other linked port and its device.

                        SUMMARY STEPS

                          1.    configure terminal

                          2.    [no] feature udld

                          3.    udld message-time seconds

                          4.    udld aggressive

                          5.    interface ethernet slot/port

                          6.    udld (enable | disable)

                          7.    show udld (ethernet slot/port | global | neighbors)

                          8.    exit

                          9.    copy running-config startup-config


                        DETAILED STEPS
                           Command or ActionPurpose
                          Step 1configure terminal


                          Example: 
                          switch# configure terminal
switch(config)#
                           

                          Enters global configuration mode.

                           
                          Step 2[no] feature udld


                          Example: 
                          switch(config)# feature udld
switch(config)#
                          switch(config)# no feature udld
switch(config)#
                           

                          Enables/Disables UDLD for the device.

                           
                          Step 3udld message-time seconds


                          Example: 
                          switch(config)# udld message-time 30
switch(config)#
                           

                          (Optional) Specifies the interval between sending UDLD messages. The range is from 7 to 90 seconds, and the default is 15 seconds.

                           
                          Step 4udld aggressive


                          Example: 
                          switch(config)# udld aggressive
switch(config)#
                           

                          Optional) Specifies UDLD mode to be aggressive.

                          Note   

                          For copper interfaces, you enter the interface command mode for those interfaces you want to configure for UDLD aggressive mode and issue this command in interface command model.

                           
                          Step 5interface ethernet slot/port


                          Example: 
                          switch(config)# interface ethernet 3/1
switch(config-if)#
                           

                          (Optional) Specifies an interface to configure, and enters interface configuration mode.

                           
                          Step 6udld (enable | disable)


                          Example: 
                          switch(config-if)# udld enable
switch(config-if)#
                           

                          (Optional) Enables UDLD on the specified copper port or disables UDLD on the specified fiber port.

                          To enable UDLD on copper ports, enter the udld enable command. To enable UDLD on fiber ports, enter the no udld disable command.

                           
                          Step 7show udld (ethernet slot/port | global | neighbors)


                          Example: 
                          switch(config)# show udld 
switch(config)#
                           

                          (Optional) Displays the UDLD status.

                           
                          Step 8exit


                          Example: 
                          switch(config-if-range)# exit
switch(config)#
                           

                          Exits the interface mode.

                           
                          Step 9copy running-config startup-config


                          Example: 
                          switch(config)# copy running-config startup-config
                           

                          (Optional) Copies the running configuration to the startup configuration.

                           

                          This example shows how to enable the UDLD for the device: 

                          switch# configure terminal 
switch(config)# feature udld
switch(config)#

                          This example shows how to set the UDLD message interval to 30 seconds: 

                          switch# configure terminal 
switch(config)# feature udld
switch(config)# udld message-time 30
switch(config)#

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

                          switch# configure terminal 
switch(config)# interface ethernet 3/1
switch(config-if-range)# no udld enable
switch(config-if-range)# exit

                          This example shows how to disable UDLD for the device: 

                          switch# configure terminal 
switch(config)# no feature udld
switch(config)# exit

                          Verifying the Basic Interface Parameters

                          You can verify the basic interface parameters by displaying their values. You can also clear the counters listed when you display the parameter values.

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

                          Command

                          Purpose

                          show cdp all

                          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 status err-disabled

                          Displays information about error-disabled interfaces.

                          show udld interface

                          Displays the UDLD status for the current interface or all interfaces.

                          show udld global

                          Displays the UDLD status for the current device.

                          show system internal pktmgr internal control

                          Displays the control message for pktmgr.

                          Monitoring the Interface Counters

                          You can display and clear interface counters using Cisco NX-OS.

                          Displaying Interface Statistics

                          You can set up to three sampling intervals for statistics collections on interfaces.

                          SUMMARY STEPS

                            1.    configure terminal

                            2.    interface ether slot/port

                            3.    load-interval counters (1 | 2 | 3) seconds

                            4.    show interface interface

                            5.    exit

                            6.    copy running-config startup-config


                          DETAILED STEPS
                             Command or ActionPurpose
                            Step 1configure terminal


                            Example: 
                            switch# configure terminal
switch(config)#
                             

                            Enters global configuration mode.

                             
                            Step 2interface ether slot/port


                            Example:
                            switch(config)# interface ether 4/1 
switch(config)#
                             

                            Specifies interface.

                             
                            Step 3load-interval counters (1 | 2 | 3) seconds


                            Example:
                            switch(config)# load-interval counters 1 100
switch(config)#
                             

                            Sets up to three sampling intervals to collect bit-rate and packet-rate statistics. The default values for each counter is as follows:

                            1—30 seconds (60 seconds for VLAN)

                            2—300 seconds

                            3—not configured

                             
                            Step 4show interface interface


                            Example:
                            switch(config)# show interface ethernet 2/2
switch#
                             

                            (Optional) Displays the interface status, which includes the counters.

                             
                            Step 5exit


                            Example:
                            switch(config-if-range)# exit
switch(config)#
                             

                            Exits the interface mode.

                             
                            Step 6copy running-config startup-config


                            Example:
                            switch(config)# copy running-config startup-config
                             

                            (Optional) Copies the running configuration to the startup configuration.

                             

                            This example shows how to set the three sample intervals for the Ethernet port 3/1:

                            switch# configure terminal 
switch(config)# interface ethernet 3/1
switch(config-if)# load-interval counter 1 60
switch(config-if)# load-interval counter 2 135
switch(config-if)# load-interval counter 3 225
switch(config-if)#

                            Clearing Interface Counters

                            You can clear the Ethernet and management interface counters by using the clear counters interface command. You can perform this task from the configuration mode or interface configuration mode.

                            SUMMARY STEPS

                              1.    clear counters interface (all | ethernet slot/port | loopback number | mgmt number | port channel channel-number)

                              2.    show interface interface

                              3.    show interface [ethernet slot/port | port channel channel-number] counters


                            DETAILED STEPS
                               Command or ActionPurpose
                              Step 1clear counters interface (all | ethernet slot/port | loopback number | mgmt number | port channel channel-number)


                              Example:
                              switch# clear counters ethernet 2/1
switch#
                               

                              Clears the interface counters.

                               
                              Step 2show interface interface


                              Example:
                              switch# show interface ethernet 2/1
switch#
                               

                              (Optional) Displays the interface status.

                               
                              Step 3show interface [ethernet slot/port | port channel channel-number] counters


                              Example:
                              switch# show interface ethernet 2/1 counters
switch#
                               

                              (Optional) Displays the interface counters.

                               

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

                              switch# clear counters interface ethernet 5/5
switch#