Cisco Nexus 6000 Series NX-OS Interfaces Configuration Guide, Release 7.x
Configuring Layer 2 Interfaces
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Contents

Configuring Layer 2 Interfaces

This chapter contains the following sections:

Information About Ethernet Interfaces

The Ethernet ports can operate as standard Ethernet interfaces connected to servers or to a LAN.

The Ethernet interfaces also support Fibre Channel over Ethernet (FCoE). FCoE allows the physical Ethernet link to carry both Ethernet and Fibre Channel traffic.

The Ethernet interfaces are enabled by default.

Interface Command

You can enable the various capabilities of the Ethernet interfaces on a per-interface basis using the interface command. When you enter the interface command, you specify the following information:

  • Interface type—All physical Ethernet interfaces use the ethernet keyword.
  • Slot number
    • Slot 1—a fixed LEM.
    • Slot 2—a fixed LEM.
    • Slot 3—a fixed LEM.
    • Slot 4—a fixed LEM.
    • Slot 5—a hot-swappable LEM (if populated)
    • Slot 6—a hot-swappable LEM (if populated)
    • Slot 7—a hot-swappable LEM (if populated)
    • Slot 8—a hot-swappable LEM (if populated)
  • QSFP-module—This is used if the port is in breakout mode. For more information about breakout mode, see Configuring Linecard Expansion Modules.
  • Port number— Port number within the group.

The interface numbering convention is extended to support use with a Cisco Nexus Fabric Extender as follows:

switch(config)# interface ethernet [chassis/]slot/port

  • Chassis ID is an optional entry that you can use to address the ports of a connected Fabric Extender. The chassis ID is configured on a physical Ethernet or EtherChannel interface on the switch to identify the Fabric Extender discovered through the interface. The chassis ID ranges from 100 to 199.
The command syntax for the Linecard Expansion Module (LEM) is the following:
  • In 40G mode: switch(config)# interface ethernet slot/port
  • In 10G mode: switch(config)# interface ethernet slot/QSFP-module/port

Information About Unified Ports

Cisco Nexus unified ports allow you to configure a physical port on a Cisco Nexus device switch as a 1/10-Gigabit Ethernet, Fibre Channel over Ethernet (FCoE), or 2-, 4-, 8-Gigabit native Fibre Channel port.

Currently, most networks have two types of switches for different types of networks. For example, LAN switches carry Ethernet traffic up to Catalyst or Nexus switches carry FC traffic from servers to MDS switches. With unified port technology, you can deploy a unified platform, unified device, and unified wire approach. Unified ports allow you to move from an existing segregated platform approach where you choose LAN and SAN port options to transition to a single, unified fabric that is transparent and consistent with existing practices and management software. A unified fabric includes the following:

  • Unified platform—Uses the same hardware platform and the same software code level and certifies it once for your LAN and SAN environments.
  • Unified device—Runs LAN and SAN services on the same platform switch. The unified device allows you to connect your Ethernet and Fibre Channel cables to the same device.
  • Unified wire—Converges LAN and SAN networks on a single converged network adapter (CNA) and connects them to your server.

A unified fabric allows you to manage Ethernet and FCoE features independently with existing Cisco tools.

Guidelines and Limitations for Unified Ports

  • Ethernet ports and Fibre Channel ports must be configured in the following order:
    • Fibre Channel ports must be configured from the last port of the module.
    • Ethernet ports must be configured from the first port of the module.
    If the order is not followed, the following errors are displayed:
    ERROR: Ethernet range starts from first port of the module
    ERROR: FC range should end on last port of the module

Unidirectional Link Detection Parameter

The Cisco-proprietary Unidirectional Link Detection (UDLD) protocol allows ports that are connected through fiber optics 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 the switch detects a unidirectional link, UDLD shuts down the affected LAN port and alerts the user. Unidirectional links can cause a variety of problems, including spanning tree topology loops.

UDLD is a Layer 2 protocol that works with the Layer 1 protocols to determine the physical status of a link. At Layer 1, autonegotiation takes care of physical signaling and fault detection. 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 and Layer 2 detections work together 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, and if 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, then UDLD at Layer 2 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.

A Cisco Nexus 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.


Note


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


The following 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 aggressive mode

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 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 frames, UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is disabled.

To prevent spanning tree loops, nonaggressive UDLD with the default interval of 15 seconds is fast enough to shut down a unidirectional link before a blocking port transitions to the forwarding state (with default spanning tree parameters).

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.

Cisco Discovery Protocol

The Cisco Discovery Protocol (CDP) is a device discovery protocol that runs over Layer 2 (the data link layer) on all Cisco-manufactured devices (routers, bridges, access servers, and switches) and allows network management applications to discover Cisco devices that are neighbors of already known devices. With CDP, network management applications can learn the device type and the Simple Network Management Protocol (SNMP) agent address of neighboring devices that are running lower-layer, transparent protocols. This feature enables applications to send SNMP queries to neighboring devices.

CDP runs on all media that support Subnetwork Access Protocol (SNAP). Because CDP runs over the data-link layer only, two systems that support different network-layer protocols can learn about each other.

Each CDP-configured device sends periodic messages to a multicast address, advertising at least one address at which it can receive SNMP messages. The advertisements also contain time-to-live, or holdtime information, which is the length of time a receiving device holds CDP information before discarding it. Each device also listens to the messages sent by other devices to learn about neighboring devices.

The switch supports both CDP Version 1 and Version 2.

Default CDP Configuration

The following table shows the default CDP configuration.

Table 2  Default CDP Configuration

Feature

Default Setting

CDP interface state

Enabled

CDP timer (packet update frequency)

60 seconds

CDP holdtime (before discarding)

180 seconds

CDP Version-2 advertisements

Enabled

Error-Disabled State

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

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 err-disabled recovery timeout for a particular err-disabled cause by changing the time variable.

The errdisable recovery cause command provides automatic recovery after 300 seconds. To change the recovery period, use the errdisable recovery interval command to specify the timeout period. You can specify 30 to 65535 seconds.

If you do not enable the err-disabled recovery for the cause, the interface stays in the err-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 err-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.

About Port Profiles

You can create a port profile that contains many interface commands and apply that port profile to a range of interfaces on the Cisco Nexus device. Port profiles can be applied to the following interface types:

  • Ethernet
  • VLAN network interface
  • Port channel

A command that is included in a port profile can be configured outside of the port profile. If the new configuration in the port profile conflicts with the configurations that exist outside the port profile, the commands configured for an interface in configuration terminal mode have higher priority than the commands in the port profile. If changes are made to the interface configuration after a port profile is attached to it, and the configuration conflicts with that in the port profile, the configurations in the interface will be given priority.

You inherit the port profile when you attach the port profile to an interface or range of interfaces, When you attach, or inherit, a port profile to an interface or range of interfaces, the switch applies all the commands in that port profile to the interfaces.

You can have one port profile inherit the settings from another port profile. Inheriting another port profile allows the initial port profile to assume all of the commands of the second, inherited, port profile that do not conflict with the initial port profile. Four levels of inheritance are supported. The same port profile can be inherited by any number of port profiles.

To apply the port profile configurations to the interfaces, you must enable the specific port profile. You can configure and inherit a port profile onto a range of interfaces prior to enabling the port profile; you then enable that port profile for the configurations to take effect on the specified interfaces.

When you remove a port profile from a range of interfaces, the switch undoes the configuration from the interfaces first and then removes the port profile link itself. When you remove a port profile, the switch checks the interface configuration and either skips the port profile commands that have been overridden by directly entered interface commands or returns the command to the default value.

If you want to delete a port profile that has been inherited by other port profiles, you must remove the inheritance before you can delete the port profile.

You can choose a subset of interfaces from which to remove a port profile from among that group of interfaces that you originally applied the profile. For example, if you configured a port profile and configured ten interfaces to inherit that port profile, you can remove the port profile from just some of the specified ten interfaces. The port profile continues to operate on the remaining interfaces to which it is applied.

If you delete a specific configuration for a specified range of interfaces using the interface configuration mode, that configuration is also deleted from the port profile for that range of interfaces only. For example, if you have a channel group inside a port profile and you are in the interface configuration mode and you delete that port channel, the specified port channel is also deleted from the port profile as well.

After you inherit a port profile on an interface or range of interfaces and you delete a specific configuration value, that port profile configuration will not operate on the specified interfaces.

If you attempt to apply a port profile to the wrong type of interface, the switch returns an error.

When you attempt to enable, inherit, or modify a port profile, the switch creates a checkpoint. If the port profile configuration fails, the switch rolls back to the prior configuration and returns an error. A port profile is never only partially applied.

Guidelines and Limitations for Port Profiles

Port profiles have the following configuration guidelines and limitations:

  • Each port profile must have a unique name across interface types and the network.
  • Commands that you enter under the interface mode take precedence over the port profile’s commands if there is a conflict. However, the port profile retains that command in the port profile.
  • The port profile’s commands take precedence over the default commands on the interface, unless the default command explicitly overrides the port profile command.
  • After you inherit a port profile onto an interface or range of interfaces, you can override individual configuration values by entering the new value at the interface configuration level. If you remove the individual configuration values at the interface configuration level, the interface uses the values in the port profile again.
  • There are no default configurations associated with a port profile.
  • A subset of commands are available under the port profile configuration mode, depending on which interface type that you specify.
  • You cannot use port profiles with Session Manager.

Debounce Timer Parameters

The port debounce time is the amount of time that an interface waits to notify the supervisor of a link going down. During this time, the interface waits to see if the link comes back up. The wait period is a time when traffic is stopped.

You can enable the debounce timer for each interface and specify the delay time in milliseconds.


Caution


When you enable the port debounce timer the link up and link down detections are delayed, resulting in a loss of traffic during the debounce period. This situation might affect the convergence and reconvergence of some protocols.


MTU Configuration

The Cisco Nexus device switch does not fragment frames. As a result, the switch cannot have two ports in the same Layer 2 domain with different maximum transmission units (MTUs). A per-physical Ethernet interface MTU is not supported. Instead, the MTU is set according to the QoS classes. You modify the MTU by setting class and policy maps.


Note


When you show the interface settings, a default MTU of 1500 is displayed for physical Ethernet interfaces and a receive data field size of 2112 is displayed for Fibre Channel interfaces.


Information About Default Interfaces

You can use the default interface feature to clear the configured parameters for both physical and logical interfaces such as the Ethernet, loopback, VLAN network, and the port-channel interface.

The default interface feature allows you to clear the existing configuration of multiple interfaces such as Ethernet, loopback, VLAN network, and port-channel interfaces. All user configuration under a specified interface will be deleted. You can optionally create a checkpoint before clearing the interface configuration so that you can later restore the deleted configuration.


Note


The default interfaces feature is supported for management interfaces but is not recommended because the device might be in an unreachable state.


Configuring Ethernet Interfaces

The section includes the following topics:

Configuring Unified Ports

Before You Begin

Confirm that you have a supported Cisco Nexus switch. Unified Ports are available on the following Cisco Nexus switches:

  • Cisco Nexus 6000
  • Cisco Nexus 6004 Unified 20 x 10GE Eth/FCoE or 8/4/2Gbps Fibre Channel

If you're configuring a unified port as Fibre Channel or FCoE, confirm that you have enabled the feature fcoe command.

Procedure
      Command or Action Purpose
    Step 1 switch# configure terminal 

    Enters global configuration mode.

     
    Step 2 switch(config) # slot slot number
     

    Identifies the slot on the switch.

     
    Step 3 switch(config-slot) # port port number type {ethernet | fc}
     
    Configures a unified port as a native Fibre Channel port and an Ethernet port.
    • type—Specifies the type of port to configure on a slot in a chassis.
    • ethernet—Specifies an Ethernet port.
    • fc—Specifies a Fibre Channel (FC) port.
    Note   

    Changing unified ports on an expansion module (GEM) requires that you power cycle the GEM card. You do not have to reboot the entire switch for changes to take effect.

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

    Copies the running configuration to the startup configuration.

     
    Step 5 switch(config-slot) # reload
     

    Reboots the switch.

     
    Step 6 switch(config) # no port port number type fc
     

    Removes the unified port.

     

    This example shows how to configure a unified port on a Cisco Nexus 5548UP switch or Cisco Nexus 5596UP switch:

    switch# configure terminal
    switch(config)# slot 1
    switch(config-slot)# port 32 type fc
    switch(config-slot)# copy running-config startup-config
    switch(config-slot)# reload
    

    This example shows how to configure 20 ports as Ethernet ports and 12 as FC ports:

    switch# configure terminal
    switch(config)# slot 1
    switch(config-slot)# port 21-32 type fc
    switch(config-slot)# copy running-config startup-config
    switch(config-slot)# reload
    

    This example shows how to configure a unified port on a Cisco N55-M16UP expansion module:

    switch# configure terminal
    switch(config)# slot 2
    switch(config-slot)# port 16 type fc
    switch(config-slot)# copy running-config startup-config
    switch(config-slot)# poweroff module 2
    switch(config-slot)# no poweroff module 2
    

    Configuring the UDLD Mode

    You can configure normal or aggressive 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.

    To use the normal UDLD mode, you must configure one of the ports for normal mode and configure the other port for the normal or aggressive mode. To use the aggressive UDLD mode, you must configure both ports for the aggressive mode.


    Note


    Before you begin, UDLD must be enabled for the other linked port and its device.


    Procedure
        Command or Action Purpose
      Step 1 switch# configure terminal
       

      Enters global configuration mode.

       
      Step 2 switch(config)# feature udld
       

      Enables UDLD for the device.

       
      Step 3 switch(config)# no feature udld
       

      Disables UDLD for the device.

       
      Step 4 switch(config)# show udld global
       

      Displays the UDLD status for the device.

       
      Step 5 switch(config)# interface type slot/port
       

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

      Note   

      If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.

       
      Step 6 switch(config-if)# udld {enable | disable | aggressive}
       

      Enables the normal UDLD mode, disables UDLD, or enables the aggressive UDLD mode.

       
      Step 7 switch(config-if)# show udld interface
       

      Displays the UDLD status for the interface.

       

      This example shows how to enable UDLD for the switch:

       
      switch# configure terminal
      switch(config)# feature udld
      
      

      This example shows how to enable the normal UDLD mode for an Ethernet port:

       
      switch# configure terminal
      switch(config)# interface ethernet 1/4
      switch(config-if)# udld enable
      
      

      This example shows how to enable the aggressive UDLD mode for an Ethernet port:

      switch# configure terminal
      switch(config)# interface ethernet 1/4
      switch(config-if)# udld aggressive
      
      

      This example shows how to disable UDLD for an Ethernet port:

       
      switch# configure terminal
      switch(config)# interface ethernet 1/4
      switch(config-if)# udld disable
      
      

      This example shows how to disable UDLD for the switch:

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

      Disabling Link Negotiation

      You can disable link negotiation using the no negotiate auto command. By default, autonegotiation is enabled on 1-Gigabit ports and disabled on 10-Gigabit ports.

      This command is equivalent to the Cisco IOS speed non-negotiate command.


      Note


      Autonegotiation configuration is not applicable on 10-Gigabit Ethernet ports. When autonegotiation is configured on a 10-Gigabit port the following error message is displayed:
      ERROR: Ethernet1/40: Configuration does not match the port capability

      Procedure
          Command or Action Purpose
        Step 1 switch# configure terminal 

        Enters global configuration mode.

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

        Selects the interface and enters interface mode.

        Note   

        If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.

         
        Step 3 switch(config-if)# no negotiate auto  

        Disables link negotiation on the selected Ethernet interface (1-Gigabit port).

         
        Step 4 switch(config-if)# negotiate auto   (Optional)

        Enables link negotiation on the selected Ethernet interface. The default for 1-Gigabit Ethernet ports is enabled.

        Note   

        This command is not applicable for 10GBASE-T ports. It should not be used on 10-GBASE-T ports.

         

        This example shows how to disable autonegotiation on a specified Ethernet interface (1-Gigabit port):

        switch# configure terminal
        switch(config)# interface ethernet 1/1
        switch(config-if)# no negotiate auto
        switch(config-if)#

        This example shows how to enable autonegotiation on a specified Ethernet interface (1-Gigabit port):

        switch# configure terminal
        switch(config)# interface ethernet 1/5
        switch(config-if)# negotiate auto
        switch(config-if)#

        Configuring the CDP Characteristics

        You can configure the frequency of Cisco Discovery Protocol (CDP) updates, the amount of time to hold the information before discarding it, and whether or not to send Version-2 advertisements.

        Procedure
            Command or Action Purpose
          Step 1 switch# configure terminal 

          Enters global configuration mode.

           
          Step 2 switch(config)# [no] cdp advertise {v1 | v2 }
           
          (Optional)

          Configures the version to use to send CDP advertisements. Version-2 is the default state.

          Use the no form of the command to return to its default setting.

           
          Step 3 switch(config)# [no] cdp format device-id {mac-address | serial-number | system-name}
           
          (Optional)

          Configures the format of the CDP device ID. The default is the system name, which can be expressed as a fully qualified domain name.

          Use the no form of the command to return to its default setting.

           
          Step 4 switch(config)# [no] cdp holdtime seconds
           
          (Optional)

          Specifies the amount of time a receiving device should hold the information sent by your device before discarding it. The range is 10 to 255 seconds; the default is 180 seconds.

          Use the no form of the command to return to its default setting.

           
          Step 5 switch(config)# [no] cdp timer seconds
           
          (Optional)

          Sets the transmission frequency of CDP updates in seconds. The range is 5 to 254; the default is 60 seconds.

          Use the no form of the command to return to its default setting.

           

          This example shows how to configure CDP characteristics:

          switch# configure terminal
          switch(config)# cdp timer 50
          switch(config)# cdp holdtime 120
          switch(config)# cdp advertise v2
          

          Enabling or Disabling CDP

          You can enable or disable CDP for Ethernet interfaces. This protocol works only when you have it enabled on both interfaces on the same link.

          Procedure
              Command or Action Purpose
            Step 1 switch# configure terminal 

            Enters global configuration mode.

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

            Enters interface configuration mode for the specified interface.

            Note   

            If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.

             
            Step 3 switch(config-if)# cdp enable
             

            Enables CDP for the interface.

            To work correctly, this parameter must be enabled for both interfaces on the same link.

             
            Step 4 switch(config-if)# no cdp enable
             

            Disables CDP for the interface.

             

            This example shows how to enable CDP for an Ethernet port:

            switch# configure terminal
            switch(config)# interface ethernet 1/4
            switch(config-if)# cdp enable
            
            

            This command can only be applied to a physical Ethernet interface.

            Enabling the Error-Disabled Detection

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

            Procedure
                Command or Action Purpose
              Step 1 switch# configure terminal 

              Enters global configuration mode.

               
              Step 2 switch(config)# errdisable detect cause {all | link-flap | loopback}  

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

               
              Step 3 switch(config)# shutdown 

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

               
              Step 4 switch(config)# no shutdown 

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

               
              Step 5 switch(config)# show interface status err-disabled 

              Displays information about err-disabled interfaces.

               
              Step 6 switch(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 err-disabled detection in all cases:

              switch# configure terminal
              switch(config)# errdisable detect cause all
              switch(config)# shutdown
              switch(config)# no shutdown
              switch(config)# show interface status err-disabled
              switch(config)# copy running-config startup-config

              Enabling the Error-Disabled Recovery

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

              Procedure
                  Command or Action Purpose
                Step 1 switch# configure terminal 

                Enters global configuration mode.

                 
                Step 2 switch(config)# errdisable recovery cause {all | udld | bpduguard | link-flap | failed-port-state | pause-rate-limit}  

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

                 
                Step 3 switch(config)# show interface status err-disabled 

                Displays information about err-disabled interfaces.

                 
                Step 4 switch(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 err-disabled recovery under all conditions:

                switch# configure terminal
                switch(config)# errdisable recovery cause all
                switch(config)# show interface status err-disabled
                switch(config)# copy running-config startup-config

                Configuring the Error-Disabled Recovery Interval

                You can use this procedure to configure the err-disabled recovery timer value. The range is from 30 to 65535 seconds. The default is 300 seconds.

                Procedure
                    Command or Action Purpose
                  Step 1 switch# configure terminal 

                  Enters global configuration mode.

                   
                  Step 2 switch(config)# errdisable recovery interval interval  

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

                   
                  Step 3 switch(config)# show interface status err-disabled  

                  Displays information about err-disabled interfaces.

                   
                  Step 4 switch(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 err-disabled recovery under all conditions:

                  switch# configure terminal
                  switch(config)# errdisable recovery interval 32
                  switch(config)# show interface status err-disabled
                  switch(config)# copy running-config startup-config

                  Configuring a Default Interface

                  Procedure
                      Command or Action Purpose
                    Step 1 switch# configure terminal 

                    Enters global configuration mode.

                     
                    Step 2 switch(config)# default interface int-if [checkpoint name] 

                    Deletes the configuration of the interface and restores the default configuration. The value of int-if can be one of the following:

                    • ethernet
                    • loopback
                    • mgmt
                    • port-channel
                    • vlan

                    Use the checkpoint keyword to store a copy of the running configuration of the interface before clearing the configuration.

                     
                    Step 3 exit
                     

                    Exits the configuration mode.

                     
                    Step 4 show interface
                     
                    (Optional)

                    Displays the interface status and information.

                     

                    This example shows how to delete the configuration of an Ethernet interface while saving a checkpoint of the running configuration for rollback purposes:

                    switch# configure terminal
                    switch(config)# show running-config interface e1/10
                    !Command: show running-config interface Ethernet1/10
                    !Time: Tue Jul 2 10:23:50 2013
                    
                    version 6.0(2)N2(1)
                    
                    interface Ethernet1/10
                    switchport mode trunk
                    channel-group 1
                    
                    default interface ethernet 3/1 checkpoint chk1
                    .......Done
                    switch(config)# show running-config interface e1/10
                    !Command: show running-config interface Ethernet1/10
                    !Time: Tue Jul 2 10:24:41 2013
                    
                    version 6.0(2)N2(1)
                    
                    interface Ethernet1/10
                    
                    switch(config)#

                    Configuring Default Interface Mode

                    Procedure
                        Command or Action Purpose
                      Step 1 switch# configure terminal 

                      Enters global configuration mode.

                       
                      Step 2 switch(config)# system default switchport 

                      Sets default interface mode.

                       

                      This example shows how to set the default interface mode:

                      switch# configure terminal
                      switch(config)# system default switchport

                      Configuring the Description Parameter

                      You can provide textual interface descriptions for the Ethernet ports.

                      Procedure
                          Command or Action Purpose
                        Step 1 switch# configure terminal 

                        Enters global configuration mode.

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

                        Enters interface configuration mode for the specified interface.

                        Note   

                        If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.

                         
                        Step 3 switch(config-if)# description test
                         

                        Specifies the description for the interface.

                         

                        This example shows how to set the interface description to Server 3 interface:

                        switch# configure terminal
                        switch(config)# interface ethernet 1/3
                        switch(config-if)# description Server 3 Interface

                        Disabling and Restarting Ethernet Interfaces

                        You can shut down and restart an Ethernet interface. This action disables all of the interface functions and marks the interface as being down on all monitoring displays.

                        Procedure
                            Command or Action Purpose
                          Step 1 switch# configure terminal 

                          Enters global configuration mode.

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

                          Enters interface configuration mode for the specified interface.

                          Note   

                          If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.

                           
                          Step 3 switch(config-if)# shutdown
                           

                          Disables the interface.

                           
                          Step 4 switch(config-if)# no shutdown
                           

                          Restarts the interface.

                           

                          This example shows how to disable an Ethernet port:

                          switch# configure terminal
                          switch(config)# interface ethernet 1/4
                          switch(config-if)# shutdown

                          This example shows how to restart an Ethernet interface:

                          switch# configure terminal
                          switch(config)# interface ethernet 1/4
                          switch(config-if)# no shutdown

                          Displaying Interface Information

                          To view configuration information about the defined interfaces, perform one of these tasks:

                          Command

                          Purpose

                          switch# show interface type slot/port

                          Displays the detailed configuration of the specified interface.

                          Note   

                          If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.

                          switch# show interface type slot/port capabilities

                          Displays detailed information about the capabilities of the specified interface. This option is available only for physical interfaces.

                          Note   

                          If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.

                          switch# show interface type slot/port transceiver

                          Displays detailed information about the transceiver connected to the specified interface. This option is available only for physical interfaces.

                          Note   

                          If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.

                          switch# show interface brief

                          Displays the status of all interfaces.

                          switch# show interface debounce

                          Displays the debounce status of all interfaces.

                          switch# show interface flowcontrol

                          Displays the detailed listing of the flow control settings on all interfaces.

                          show port--profile

                          Displays information about the port profiles.

                          The show interface command is invoked from EXEC mode and displays the interface configurations. Without any arguments, this command displays the information for all the configured interfaces in the switch.

                          This example shows how to display the physical Ethernet interface:

                          switch# show interface ethernet 1/1
                            Ethernet1/1 is up
                            Hardware is 1000/10000 Ethernet, address is 000d.eca3.5f08 (bia 000d.eca3.5f08)
                            MTU 1500 bytes, BW 10000000 Kbit, DLY 10 usec,
                               reliability 255/255, txload 190/255, rxload 192/255
                            Encapsulation ARPA
                            Port mode is trunk
                            full-duplex, 10 Gb/s, media type is 1/10g
                            Input flow-control is off, output flow-control is off
                            Auto-mdix is turned on
                            Rate mode is dedicated
                            Switchport monitor is off
                            Last clearing of "show interface" counters never
                            5 minute input rate 942201806 bytes/sec, 14721892 packets/sec
                            5 minute output rate 935840313 bytes/sec, 14622492 packets/sec
                            Rx
                              129141483840 input packets 0 unicast packets 129141483847 multicast packets
                              0 broadcast packets 0 jumbo packets 0 storm suppression packets
                              8265054965824 bytes
                              0 No buffer 0 runt 0 Overrun
                              0 crc 0 Ignored 0 Bad etype drop
                              0 Bad proto drop
                            Tx
                              119038487241 output packets 119038487245 multicast packets
                             0 broadcast packets 0 jumbo packets
                              7618463256471 bytes
                              0 output CRC 0 ecc
                              0 underrun 0 if down drop     0 output error 0 collision 0 deferred
                              0 late collision 0 lost carrier 0 no carrier
                              0 babble
                              0 Rx pause 8031547972 Tx pause 0 reset

                          This example shows how to display the physical Ethernet capabilities:

                          switch# show interface ethernet 1/1 capabilities
                          Ethernet1/1
                            Model:                 734510033
                            Type:                  10Gbase-(unknown)
                            Speed:                 1000,10000
                            Duplex:                full
                            Trunk encap. type:     802.1Q
                            Channel:               yes
                            Broadcast suppression: percentage(0-100)
                            Flowcontrol:           rx-(off/on),tx-(off/on)
                            Rate mode:             none
                            QOS scheduling:        rx-(6q1t),tx-(1p6q0t)
                            CoS rewrite:           no
                            ToS rewrite:           no
                            SPAN:                  yes
                            UDLD:                  yes
                            Link Debounce:         yes
                            Link Debounce Time:    yes
                            MDIX:                  no
                            FEX Fabric:            yes
                          

                          This example shows how to display the physical Ethernet transceiver:

                          switch# show interface ethernet 1/1 transceiver
                          Ethernet1/1
                              sfp is present
                              name is CISCO-EXCELIGHT
                              part number is SPP5101SR-C1
                              revision is A
                              serial number is ECL120901AV
                              nominal bitrate is 10300 MBits/sec
                              Link length supported for 50/125mm fiber is 82 m(s)
                              Link length supported for 62.5/125mm fiber is 26 m(s)
                              cisco id is --
                              cisco extended id number is 4

                          This example shows how to display a brief interface status (some of the output has been removed for brevity):

                          switch# show interface brief
                          
                          --------------------------------------------------------------------------------
                          Ethernet      VLAN   Type Mode   Status  Reason                   Speed     Port
                          Interface                                                                   Ch #
                          --------------------------------------------------------------------------------
                          Eth1/1        200    eth  trunk  up      none                        10G(D) --
                          Eth1/2        1      eth  trunk  up      none                        10G(D) --
                          Eth1/3        300    eth  access down    SFP not inserted            10G(D) --
                          Eth1/4        300    eth  access down    SFP not inserted            10G(D) --
                          Eth1/5        300    eth  access down    Link not connected         1000(D) --
                          Eth1/6        20     eth  access down    Link not connected          10G(D) --
                          Eth1/7        300    eth  access down    SFP not inserted            10G(D) --
                          ...
                          

                          This example shows how to display the link debounce status (some of the output has been removed for brevity):

                          switch# show interface debounce
                          
                          --------------------------------------------------------------------------------
                          Port          Debounce time   Value(ms)
                          --------------------------------------------------------------------------------
                          ...
                          Eth1/1        enable               100
                          Eth1/2        enable               100
                          Eth1/3        enable               100
                          ...
                          

                          This example shows how to display the CDP neighbors:


                          Note


                          The default device ID field for CDP advertisement is the hostname and serial number, as in the example above.


                          switch# show cdp neighbors
                          Capability Codes: R - Router, T - Trans-Bridge, B - Source-Route-Bridge
                                            S - Switch, H - Host, I - IGMP, r - Repeater,
                                            V - VoIP-Phone, D - Remotely-Managed-Device,
                                            s - Supports-STP-Dispute
                          Device ID              Local Intrfce   Hldtme  Capability  Platform      Port ID
                          d13-dist-1               mgmt0           148     S I      WS-C2960-24TC  Fas0/9
                          n5k(FLC12080012)         Eth1/5          8       S I s    N5K-C5020P-BA  Eth1/5

                          Default Physical Ethernet Settings

                          The following table lists the default settings for all physical Ethernet interfaces:

                          Parameter

                          Default Setting

                          Debounce

                          Enable, 100 milliseconds

                          Duplex

                          Auto (full-duplex)

                          Encapsulation

                          ARPA

                          MTU1

                          1500 bytes

                          Port Mode

                          Access

                          Speed

                          Auto (10000)

                          1 MTU cannot be changed per-physical Ethernet interface. You modify MTU by selecting maps of QoS classes.