Interface Configuration


Note For complete syntax and usage information for the commands used in this chapter, see these publications:

http://www.cisco.com/en/US/products/ps11846/prod_command_reference_list.html

  • Cisco IOS Release 15.1SY supports only Ethernet interfaces. Cisco IOS Release 15.1SY does not support any WAN features or commands.


 


Tip For additional information about Cisco Catalyst 6500 Series Switches (including configuration examples and troubleshooting information), see the documents listed on this page:

http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html

Participate in the Technical Documentation Ideas forum


 

Information About Interface Configuration

Many features in the software are enabled on a per-interface basis. When you enter the interface command, you must specify the following information:

  • Interface type:

Fast Ethernet (use the fastethernet keyword)

Gigabit Ethernet (use the gigabitethernet keyword)

10-Gigabit Ethernet (use the tengigabitethernet keyword)

  • Slot number—The slot in which the module is installed. On switches supported by Cisco IOS Release 15.1SY, slots are numbered starting with 1 from top to bottom.
  • Port number—The physical port number on the module. On switches supported by Cisco IOS Release 15.1SY, the port numbers always begin with 1. When facing the rear of the switch, ports are numbered from the left to the right.

You can identify ports from the physical location. You also can use show commands to display information about a specific port, or all the ports.

See this document for information about the interface command:

http://www.cisco.com/en/US/docs/ios-xml/ios/interface/command/ir-i1.html#GUID-0D6BDFCD-3FBB-4D26-A274-C1221F8592DF

How to Configure a Range of Interfaces

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. See this document for information about the interface range command:

http://www.cisco.com/en/US/docs/ios-xml/ios/interface/command/ir-i1.html#GUID-8EC4EF91-F929-45F8-95CA-E4C9A9724FFF

How to Define and Use Interface-Range Macros

You can define an interface-range macro to automatically select a range of interfaces for configuration. Before you can use the macro keyword in the interface range macro command string, you must define the macro.

To define an interface-range macro, perform this task:

 

Command
Purpose

Router(config)# define interface-range macro_name { vlan vlan_ID - vlan_ID } | { type slot/port - port } [, { type slot/port - port }]

Defines the interface-range macro and save it in NVRAM.

This example shows how to define an interface-range macro named enet_list to select Gigabit Ethernet ports 1/1 through 1/4:

Router(config)# define interface-range enet_list gigabitethernet 1/1 - 4
 

To show the defined interface-range macro configuration, perform this task:

 

Command
Purpose

Router# show running-config

Shows the defined interface-range macro configuration.

This example shows how to display the defined interface-range macro named enet_list:

Router# show running-config | include define
define interface-range enet_list GigabitEthernet1/1 - 4
Router#
 

To use an interface-range macro in the interface range command, perform this task:

 

Command
Purpose

Router(config)# interface range macro macro_name

Selects the interface range to be configured using the values saved in a named interface-range macro.

This example shows how to change to the interface-range configuration mode using the interface-range macro enet_list:

Router(config)# interface range macro enet_list
Router(config-if)#

How to Configure Optional Interface Features

Configuring Ethernet Interface Speed and Duplex Mode

Speed and Duplex Mode Configuration Guidelines

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

  • You cannot set the Ethernet port speed to auto (the no speed command) if the duplex mode in not set to auto (the no duplex command).
  • If you configure an Ethernet port speed to a value other than auto (for example, 10, 100, or 1000 Mbps), configure the connecting port to match. Do not configure the connecting port to negotiate the speed.
  • If you manually configure the Ethernet port speed to either 10 Mbps or 100 Mbps, the switch prompts you to also configure the duplex mode on the port.

Note A LAN port cannot automatically negotiate 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 during the reconfiguration.

Configuring the Ethernet Interface Speed


Note If you configure the Ethernet port speed to auto on a 10/100/1000-Mbps Ethernet port, both speed and duplex are autonegotiated. 10-Gigabit Ethernet ports do not support autonegotiation.


To configure the port speed for a 10/100/1000-Mbps Ethernet port, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface gigabitethernet slot/port

Selects the Ethernet port to be configured.

Step 2

Router(config-if)# speed { 10 | 100 | 1000 | { auto [ 10 100 [ 1000 ]]}}

Configures the speed of the Ethernet interface.

When configuring the port speed for a 10/100/1000-Mbps Ethernet port, note the following:

  • Enter the auto 10 100 keywords to restrict the negotiated speed to 10-Mbps or 100-Mbps.
  • The auto 10 100 1000 keywords have the same effect as the auto keyword by itself.

This example shows how to configure the speed to 100 Mbps on the Gigabit Ethernet port 1/4:

Router(config)# interface gigabitethernet 1/4
Router(config-if)# speed 100

Setting the Interface Duplex Mode


Note 10-Gigabit Ethernet and Gigabit Ethernet are full duplex only. You cannot change the duplex mode on 10-Gigabit Ethernet or Gigabit Ethernet ports or on a 10/100/1000-Mps port configured for Gigabit Ethernet.

  • If you set the port speed to auto on a 10/100/1000-Mbps Ethernet port, both speed and duplex are autonegotiated. You cannot change the duplex mode of autonegotiation ports.


 

To set the duplex mode of an Ethernet or Gigabit Ethernet port, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface gigabitethernet slot/port

Selects the Ethernet port to be configured.

Step 2

Router(config-if)# duplex [ auto | full | half ]

Sets the duplex mode of the Ethernet port.

This example shows how to set the duplex mode to full on Gigabit Ethernet port 1/4:

Router(config)# interface gigabitethernet 1/4
Router(config-if)# duplex full

Configuring Link Negotiation on Gigabit Ethernet Ports


Note Link negotiation does not negotiate port speed.


On Gigabit Ethernet ports, link negotiation exchanges flow-control parameters, remote fault information, and duplex information. Link negotiation is enabled by default.

The ports on both ends of a link must have the same setting. The link will not come up if the ports at each end of the link are set inconsistently (link negotiation enabled on one port and disabled on the other port).

Table 10-1 shows the four possible link negotiation configurations and the resulting link status for each configuration.

 

Table 10-1 Link Negotiation Configuration and Possible Link Status

Link Negotiation State
Link Status
Local Port
Remote Port
Local Port
Remote Port

Off

Off

Up

Up

On

On

Up

Up

Off

On

Up

Down

On

Off

Down

Up

To configure link negotiation on a port, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface gigabitethernet slot/port

Selects the port to be configured.

Step 2

Router(config-if)# speed nonegotiate

Disables link negotiation.

This example shows how to enable link negotiation on Gigabit Ethernet port 1/4:

Router(config)# interface gigabitethernet 1/4
Router(config-if)# no speed nonegotiate

Displaying the Speed and Duplex Mode Configuration

To display the speed and duplex mode configuration for a port, perform this task:

 

Command
Purpose

Router# show interfaces type slot/port [ transceiver properties ]

Displays the speed and duplex mode configuration. To display autonegotiation status for speed and duplex, add the transceiver properties option.

Configuring Jumbo Frame Support

Information about Jumbo Frame Support

Jumbo Frame Support Overview

A jumbo frame is a frame larger than the default Ethernet size. You enable jumbo frame support by configuring a larger-than-default maximum transmission unit (MTU) size on a port or VLAN interface and configuring the global LAN port MTU size.


Note Jumbo frame support fragments routed traffic in software on the route processor (RP).

  • Jumbo frame support does not fragment bridged traffic.


 

Bridged and Routed Traffic Size Check at Ingress 10/100, and 100 Mbps Ethernet and 10-Gigabit Ethernet Ports

Jumbo frame support compares ingress traffic size with the global LAN port MTU size at ingress 10/100, and 100 Mbps Ethernet and 10-Gigabit Ethernet LAN ports that have a nondefault MTU size configured. The port drops traffic that is oversized. You can configure the global LAN port MTU size (see the “Configuring the Global Egress LAN Port MTU Size” section).

Bridged and Routed Traffic Size Check at Ingress Gigabit Ethernet Ports

Gigabit Ethernet LAN ports configured with a nondefault MTU size accept frames containing packets of any size larger than 64 bytes. With a nondefault MTU size configured, Gigabit Ethernet LAN ports do not check for oversize ingress frames.

Routed Traffic Size Check on the PFC

For traffic that needs to be routed, Jumbo frame support on the PFC compares traffic sizes to the configured MTU sizes and provides Layer 3 switching for jumbo traffic between interfaces configured with MTU sizes large enough to accommodate the traffic. Between interfaces that are not configured with large enough MTU sizes, if the “do not fragment bit” is not set, the PFC sends the traffic to the RP to be fragmented and routed in software. If the “do not fragment bit” is set, the PFC drops the traffic.

Bridged and Routed Traffic Size Check at Egress 10, 10/100, and 100 Mbps Ethernet Ports

10, 10/100, and 100 Mbps Ethernet LAN ports configured with a nondefault MTU size transmit frames containing packets of any size larger than 64 bytes. With a nondefault MTU size configured, 10, 10/100, and 100 Mbps Ethernet LAN ports do not check for oversize egress frames.

Bridged and Routed Traffic Size Check at Egress Gigabit Ethernet and 10-Gigabit Ethernet Ports

Jumbo frame support compares egress traffic size with the global egress LAN port MTU size at egress Gigabit Ethernet and 10-Gigabit Ethernet LAN ports that have a nondefault MTU size configured. The port drops traffic that is oversized. You can configure the global LAN port MTU size (see the “Configuring the Global Egress LAN Port MTU Size” section).

Nondefault MTU Sizes on Ethernet Ports

Ethernet Port Overview

Configuring a nondefault MTU size on a 10, 10/100, or 100 Mbps Ethernet port limits ingress packets to the global LAN port MTU size and permits egress traffic of any size larger than 64 bytes.

Configuring a nondefault MTU size on a Gigabit Ethernet port permits ingress packets of any size larger than 64 bytes and limits egress traffic to the global LAN port MTU size.

Configuring a nondefault MTU size on a 10-Gigabit Ethernet port limits ingress and egress packets to the global LAN port MTU size.

You can configure the MTU size on any Ethernet port.

Layer 3 Ethernet Ports

On a Layer 3 port, you can configure an MTU size on each Layer 3 Ethernet port that is different than the global LAN port MTU size.


Note Traffic through a Layer 3 Ethernet LAN port that is configured with a nondefault MTU size is also subject to the global LAN port MTU size (see the “Configuring the Global Egress LAN Port MTU Size” section).


Layer 2 Ethernet Ports

On a Layer 2 port, you can only configure an MTU size that matches the global LAN port MTU size (see the “Configuring the Global Egress LAN Port MTU Size” section).

VLAN Interfaces

You can configure a different MTU size on each Layer 3 VLAN interface. Configuring a nondefault MTU size on a VLAN interface limits traffic to the nondefault MTU size. You can configure the MTU size on VLAN interfaces to support jumbo frames.

Configuring MTU Sizes

Configuring the MTU Size

To configure the MTU size, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface {{ vlan vlan_ID } | {{ type slot/port } | { port-channel port_channel_number } slot/port }}

Selects the interface to configure.

Step 2

Router(config-if)# mtu mtu_size

Configures the MTU size.

Step 3

Router(config-if)# end

Exits configuration mode.

When configuring the MTU size, note the following information:

  • For VLAN interfaces and Layer 3 Ethernet ports, supported MTU values are from 64 to 9216 bytes.
  • For Layer 2 Ethernet ports, you can configure only the global egress LAN port MTU size (see the “Configuring the Global Egress LAN Port MTU Size” section).
  • MTU size on a Layer 2 interface is always set to maximum. If you reconfigure the MTU size to enable jumbo frame support, MTU size does not get updated in the MTU hardware table for L2 interface at the egress. The interface (L2) MTU size check happens only at the ingress port.

This example shows how to configure the MTU size on Gigabit Ethernet port 1/2:

Router# configure terminal
Router(config)# interface gigabitethernet 1/2
Router(config-if)# mtu 9216
Router(config-if)# end
 

This example shows how to verify the configuration:

Router# show interface gigabitethernet 1/2
GigabitEthernet1/2 is administratively down, line protocol is down
Hardware is C6k 1000Mb 802.3, address is 0030.9629.9f88 (bia 0030.9629.9f88)
MTU 9216 bytes, BW 1000000 Kbit, DLY 10 usec,
<...Output Truncated...>
Router#

Configuring the Global Egress LAN Port MTU Size

To configure the global egress LAN port MTU size, perform this task:

 

Command
Purpose

Step 1

Router(config)# system jumbomtu mtu_size

Configures the global egress LAN port MTU size.

Note Because it would change all the interface MTU sizes to the default (1500), rather than to any configured nondefault interface MTU size, do not use the system jumbomtu command to set the MTU size to 1500. (CSCtq52016)

Step 2

Router(config)# end

Exits configuration mode.

Configuring IEEE 802.3x Flow Control

Gigabit Ethernet and 10-Gigabit Ethernet ports use flow control to stop the transmission of frames to the port for a specified time; other Ethernet ports use flow control to respond to flow-control requests.

If a Gigabit Ethernet or 10-Gigabit Ethernet port receive buffer becomes full, the port can be configured to transmit an IEEE 802.3x pause frame that requests the remote port to delay sending frames for a specified time. All Ethernet ports can can be configured to respond to IEEE 802.3x pause frames from other devices.

To configure flow control on an Ethernet port, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface type slot/port

Selects the port to configure.

Step 2

Router(config-if)# flowcontrol { receive | send } { desired | off | on }

Configures a port to send or respond to pause frames.

When configuring flow control, note the following information:

  • Because auto negotiation does not work on 10 Gigbit Ethernet fiber optic ports, they respond to pause frames by default. On 10 Gigbit Ethernet fiber optic ports, the flow-control operational mode is always the same as administrative mode.
  • When configuring how a port responds to pause frames, note the following information:

For a Gigabit Ethernet port, when the configuration of a remote port is unknown, you can use the receive desired keywords to configure the Gigabit Ethernet port to respond to received pause frames. (Supported only on Gigabit Ethernet ports.)

Use the receive on keywords to configure a port to respond to received pause frames.

Use the receive off keywords to configure a port to ignore received pause frames.

  • When configuring transmission of pause frames on a port, note the following information:

For a Gigabit Ethernet port, when the configuration of the remote ports is unknown, you can use the send desired keywords to configure the Gigabit Ethernet port to send pause frames. (Supported only on Gigabit Ethernet ports.)

Use the send on keywords to configure a port to send pause frames.

Use the send off keywords to configure a port not to send pause frames.

This example shows how to turn on receive flow control and how to verify the flow-control configuration:

Router# configure terminal
Router(config)# interface gigabitethernet 1/2
Router(config-if)# flowcontrol receive on
Router(config-if)# end
Router# show interfaces flowcontrol
 
Interface Send Receive
Gi1/1 Desired OFF
Gi1/2 Desired ON
<output truncated>

Configuring the Port Debounce Timer

The port debounce timer delays notification of a link change, which can decrease traffic loss due to network reconfiguration. You can configure the port debounce timer separately on each LAN port.


Caution Enabling the port debounce timer causes link down detections to be delayed, resulting in loss of traffic during the debouncing period. This situation might affect the convergence and reconvergence of some Layer 2 and Layer 3 protocols.

To configure the debounce timer on a port, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface type slot/port

Selects the port to configure.

Step 2

Router(config-if)# link debounce [ time debounce_time ]

Configures the debounce timer.

When configuring the debounce timer on a port, note the following information:

  • The time keyword is supported only on fiber 1000 Mpbs or faster Ethernet ports.
  • You can increase the port debounce timer value in increments of 100 milliseconds up to 5000 milliseconds on ports operating at 1000 Mpbs over copper media.
  • The debounce timer recognizes 10-Gbps copper media and detects media-only changes.

Table 10-2 lists the time delay that occurs before notification of a link change.

 

Table 10-2 Default Port Debounce Timer Delay Times

Port Type
Debounce Timer Disabled
Debounce Timer Enabled

Ports operating at 10 Mpbs or 100 Mbps:

300 milliseconds

3100 milliseconds

Ports operating at 1000 Mpbs or 10 Gbps over copper media:

300 milliseconds

3100 milliseconds

Ports operating at 1000 Mpbs or 10 Gbps over fiber media:

10 milliseconds

100 milliseconds

Note The show interfaces debounce command does not display the default value for 10-GigabitEthernet ports when the port debounce timer is disabled.


Note On all 10-Gigabit Ethernet ports, the Debounce Timer Disabled value is 10 milliseconds and the Debounce Timer Enabled value is 100 milliseconds.


This example shows how to enable the port debounce timer on Gigabit Ethernet port 1/12:

Router(config)# interface gigabitethernet 1/12
Router(config-if)# link debounce
Router(config-if)# end
 

This example shows how to display the port debounce timer settings:

Router# show interfaces debounce | include enable
Gi1/12 enable 3100

Information About Online Insertion and Removal

The online insertion and removal (OIR) feature allows you to remove and replace modules while the system is online. You can shut down the modules before removal and restart it after insertion without causing other software or interfaces to shut down.


Note Do not remove or install more than one module at a time. After you remove or install a module, check the LEDs before continuing. For module LED descriptions, see the Catalyst 6500 Series Switch Installation Guide.


When a module has been removed or installed, the switch stops processing traffic for the module and scans the system for a configuration change. Each interface type is verified against the system configuration, and then the system runs diagnostics on the new module. There is no disruption to normal operation during module insertion or removal.

The switch can bring only an identical replacement module online. To support OIR of an identical module, the module configuration is not removed from the running-config file when you remove a module.

If the replacement module is different from the removed module, you must configure it before the switch can bring it online.

Layer 2 MAC addresses are stored in an EEPROM, which allows modules to be replaced online without requiring the system to update switching tables and data structures. Regardless of the types of modules installed, the Layer 2 MAC addresses do not change unless you replace the supervisor engine. If you do replace the supervisor engine, the Layer 2 MAC addresses of all ports change to those specified in the address allocator on the new supervisor engine.

How to Monitor and Maintain Interfaces

Monitoring Interface Status

The software contains commands that you can enter at the EXEC prompt to display information about the interface including the version of the software and the hardware and statistics about interfaces. The following table lists some of the interface monitoring commands. (You can display the complete list of show commands by using the show ? command at the EXEC prompt.) These commands are described in the Cisco IOS Interface Command Reference publication.

To display information about the interface, perform these tasks:

 

Command
Purpose

Router# show ibc

Displays current internal status information.

Router# show eobc

Displays current internal out-of-band information.

Router# show interfaces [ type slot/port ]

Displays the status and configuration of all or a specific interface.

Router# show running-config

Displays the currently running configuration.

Router# show rif

Displays the current contents of the routing information field (RIF) cache.

Router# show protocols [ type slot/port ]

Displays the global (system-wide) and interface-specific status of any configured protocol.

Router# show version

Displays the hardware configuration, software version, the names and sources of configuration files, and the boot images.

Clearing Counters on an Interface

To clear the interface counters shown with the show interfaces command, perform this task:

 

Command
Purpose

Router# clear counters {{ vlan vlan_ID } | { type slot/port } | { port-channel channel_ID }}

Clears interface counters.

This example shows how to clear and reset the counters on Gigabit Ethernet port 1/5:

Router# clear counters gigabitethernet 1/5
Clear "show interface" counters on this interface [confirm] y
*Sep 30 08:42:55: %CLEAR-5-COUNTERS: Clear counter on interface GigabitEthernet1/5
 

The clear counters command clears all the current counters from the interface unless the optional arguments specify a specific interface.


Note The clear counters command clears counters displayed with the EXEC show interfaces command, not counters retrieved using SNMP.


Resetting an Interface

To reset an interface, perform this task:

 

Command
Purpose

Router# clear interface type slot/port

Resets an interface.

This example shows how to reset Gigabit Ethernet port 1/5:

Router# clear interface gigabitethernet 1/5

Shutting Down and Restarting an Interface

You can shut down an interface, which disables all functions on the specified interface and shows the interface as unavailable on all monitoring command displays. This information is communicated to other network servers through all dynamic routing protocols. The interface is not included in any routing updates.

To shut down an interface and then restart it, perform this task:

 

Command
Purpose

Step 1

Router(config)# interface {{ vlan vlan_ID } | { type slot/port } | { port-channel channel_ID }}

Selects the interface to be configured.

Step 2

Router(config-if)# shutdown

Shuts down the interface.

Step 3

Router(config-if)# no shutdown

Reenables the interface.

This example shows how to shut down Gigabit Ethernet port 1/5:

Router(config)# interface gigabitethernet 1/5
Router(config-if)# shutdown
Router(config-if)#

Note The link state messages (LINK-3-UPDOWN and LINEPROTO-5-UPDOWN) are disabled by default. Enter the logging event link status command on each interface where you want the messages enabled.


This example shows how to reenable Gigabit Ethernet port 1/5:

Router(config-if)# no shutdown
Router(config-if)#
 

To check if an interface is disabled, enter the EXEC show interfaces command. An interface that has been shut down is shown as administratively down in the show interfaces command display.

How to Check Cable Status with the TDR

You can check the status of copper cables using the time domain reflectometer (TDR). The TDR detects a cable fault by sending a signal through the cable and reading the signal that is reflected back to it. All or part of the signal can be reflected back by any number of cable defects or by the end of the cable itself.

Use the TDR to determine if the cabling is at fault if you cannot establish a link. This test is especially important when replacing an existing switch, upgrading to Gigabit Ethernet, or installing new cables.


Note TDR can test cables up to a maximum length of 115 meters.

  • TDR results are not meaningful for a link that is operating successfully.
  • The port must be up before running the TDR test. If the port is down, you cannot enter the test cable-diagnostics tdr command successfully, and the following message is displayed:
Router# test cable-diagnostics tdr interface gigabitethernet2/12
% Interface Gi2/12 is administratively down
% Use 'no shutdown' to enable interface before TDR test start.


 

To start or stop the TDR test, perform this task:

 

Command
Purpose

test cable-diagnostics tdr interface { interface interface_number }

Starts or stops the TDR test.

This example shows how to run the TDR-cable diagnostics:

Router # test cable-diagnostics tdr interface gigabitethernet2/1
TDR test started on interface Gi2/1
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.
Router #


Tip For additional information about Cisco Catalyst 6500 Series Switches (including configuration examples and troubleshooting information), see the documents listed on this page:

http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html

Participate in the Technical Documentation Ideas forum