Software Configuration Guide, Cisco IOS Release 15.2(2)E (Catalyst 2960, 2960-S, 2960-SF and 2960-Plus Switches)
Troubleshooting the Software Configuration
Downloads: This chapterpdf (PDF - 1.54MB) The complete bookPDF (PDF - 13.78MB) | The complete bookePub (ePub - 3.49MB) | Feedback

Troubleshooting the Software Configuration

Contents

Troubleshooting the Software Configuration

This chapter describes how to identify and resolve software problems related to the Cisco IOS software on the switch. Depending on the nature of the problem, you can use the command-line interface (CLI), Device Manager, or Network Assistant to identify and solve problems.

Additional troubleshooting information, such as LED descriptions, is provided in the hardware installation guide.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http:/​/​www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Information About Troubleshooting the Software Configuration

Software Failure on a Switch

Switch software can be corrupted during an upgrade by downloading the incorrect file to the switch, and by deleting the image file. In all of these cases, the switch does not pass the power-on self-test (POST), and there is no connectivity.

Lost or Forgotten Password on a Switch

The default configuration for the switch allows an end user with physical access to the switch to recover from a lost password by interrupting the boot process during power-on and by entering a new password. These recovery procedures require that you have physical access to the switch.


Note


On these switches, a system administrator can disable some of the functionality of this feature by allowing an end user to reset a password only by agreeing to return to the default configuration. If you are an end user trying to reset a password when password recovery has been disabled, a status message reminds you to return to the default configuration during the recovery process.


Power over Ethernet Ports

A Power over Ethernet (PoE) switch port automatically supplies power to one of these connected devices if the switch detects that there is no power on the circuit:

  • a Cisco pre-standard powered device (such as a Cisco IP Phone or a Cisco Aironet Access Point)
  • an IEEE 802.3af-compliant powered device
  • an IEEE 802.3at-compliant powered device

A powered device can receive redundant power when it is connected to a PoE switch port and to an AC power source. The device does not receive redundant power when it is only connected to the PoE port.

After the switch detects a powered device, the switch determines the device power requirements and then grants or denies power to the device. The switch can also detect the real-time power consumption of the device by monitoring and policing the power usage.

For more information, see the "Configuring PoE" chapter in the .

Disabled Port Caused by Power Loss

If a powered device (such as a Cisco IP Phone 7910) that is connected to a PoE switch port and powered by an AC power source loses power from the AC power source, the device might enter an error-disabled state. To recover from an error-disabled state, enter the shutdown interface configuration command, and then enter the no shutdown interface command. You can also configure automatic recovery on the switch to recover from the error-disabled state.

On a switch, the errdisable recovery cause loopback and the errdisable recovery interval seconds global configuration commands automatically take the interface out of the error-disabled state after the specified period of time.

Disabled Port Caused by False Link-Up

If a Cisco powered device is connected to a port and you configure the port by using the power inline never interface configuration command, a false link-up can occur, placing the port into an error-disabled state. To take the port out of the error-disabled state, enter the shutdown and the no shutdown interface configuration commands.

You should not connect a Cisco powered device to a port that has been configured with the power inline never command.

Ping

The switch supports IP ping, which you can use to test connectivity to remote hosts. Ping sends an echo request packet to an address and waits for a reply. Ping returns one of these responses:

  • Normal response—The normal response (hostname is alive) occurs in 1 to 10 seconds, depending on network traffic.
  • Destination does not respond—If the host does not respond, a no-answer message is returned.
  • Unknown host—If the host does not exist, an unknown host message is returned.
  • Destination unreachable—If the default gateway cannot reach the specified network, a destination-unreachable message is returned.
  • Network or host unreachable—If there is no entry in the route table for the host or network, a network or host unreachable message is returned.

Layer 2 Traceroute

The Layer 2 traceroute feature allows the switch to identify the physical path that a packet takes from a source device to a destination device. Layer 2 traceroute supports only unicast source and destination MAC addresses. Traceroute finds the path by using the MAC address tables of the switches in the path. When the switch detects a device in the path that does not support Layer 2 traceroute, the switch continues to send Layer 2 trace queries and lets them time out.

The switch can only identify the path from the source device to the destination device. It cannot identify the path that a packet takes from source host to the source device or from the destination device to the destination host.

Layer 2 Traceroute Guidelines

  • Cisco Discovery Protocol (CDP) must be enabled on all the devices in the network. For Layer 2 traceroute to function properly, do not disable CDP. If any devices in the physical path are transparent to CDP, the switch cannot identify the path through these devices.
  • A switch is reachable from another switch when you can test connectivity by using the ping privileged EXEC command. All switches in the physical path must be reachable from each other.
  • The maximum number of hops identified in the path is ten.
  • You can enter the traceroute mac or the traceroute mac ip privileged EXEC command on a switch that is not in the physical path from the source device to the destination device. All switches in the path must be reachable from this switch.
  • The traceroute mac command output shows the Layer 2 path only when the specified source and destination MAC addresses belong to the same VLAN. If you specify source and destination MAC addresses that belong to different VLANs, the Layer 2 path is not identified, and an error message appears.
  • If you specify a multicast source or destination MAC address, the path is not identified, and an error message appears.
  • If the source or destination MAC address belongs to multiple VLANs, you must specify the VLAN to which both the source and destination MAC addresses belong. If the VLAN is not specified, the path is not identified, and an error message appears.
  • The traceroute mac ip command output shows the Layer 2 path when the specified source and destination IP addresses belong to the same subnet. When you specify the IP addresses, the switch uses the Address Resolution Protocol (ARP) to associate the IP addresses with the corresponding MAC addresses and the VLAN IDs.
    • If an ARP entry exists for the specified IP address, the switch uses the associated MAC address and identifies the physical path.
    • If an ARP entry does not exist, the switch sends an ARP query and tries to resolve the IP address. If the IP address is not resolved, the path is not identified, and an error message appears.
  • When multiple devices are attached to one port through hubs (for example, multiple CDP neighbors are detected on a port), the Layer 2 traceroute feature is not supported. When more than one CDP neighbor is detected on a port, the Layer 2 path is not identified, and an error message appears.
  • This feature is not supported in Token Ring VLANs.

IP Traceroute

You can use IP traceroute to identify the path that packets take through the network on a hop-by-hop basis. The command output displays all network layer (Layer 3) devices, such as routers, that the traffic passes through on the way to the destination.

Your switches can participate as the source or destination of the traceroute privileged EXEC command and might or might not appear as a hop in the traceroute command output. If the switch is the destination of the traceroute, it is displayed as the final destination in the traceroute output. Intermediate switches do not show up in the traceroute output if they are only bridging the packet from one port to another within the same VLAN. However, if the intermediate switch is a multilayer switch that is routing a particular packet, this switch shows up as a hop in the traceroute output.

The traceroute privileged EXEC command uses the Time To Live (TTL) field in the IP header to cause routers and servers to generate specific return messages. Traceroute starts by sending a User Datagram Protocol (UDP) datagram to the destination host with the TTL field set to 1. If a router finds a TTL value of 1 or 0, it drops the datagram and sends an Internet Control Message Protocol (ICMP) time-to-live-exceeded message to the sender. Traceroute finds the address of the first hop by examining the source address field of the ICMP time-to-live-exceeded message.

To identify the next hop, traceroute sends a UDP packet with a TTL value of 2. The first router decrements the TTL field by 1 and sends the datagram to the next router. The second router sees a TTL value of 1, discards the datagram, and returns the time-to-live-exceeded message to the source. This process continues until the TTL is incremented to a value large enough for the datagram to reach the destination host (or until the maximum TTL is reached).

To learn when a datagram reaches its destination, traceroute sets the UDP destination port number in the datagram to a very large value that the destination host is unlikely to be using. When a host receives a datagram destined to itself containing a destination port number that is unused locally, it sends an ICMP port-unreachable error to the source. Because all errors except port-unreachable errors come from intermediate hops, the receipt of a port-unreachable error means that this message was sent by the destination port.

Time Domain Reflector Guidelines

You can use the Time Domain Reflector (TDR) feature to diagnose and resolve cabling problems. When running TDR, a local device sends a signal through a cable and compares the reflected signal to the initial signal.

TDR is supported only on 10/100/1000 copper Ethernet ports. It is not supported on 10-Gigabit Ethernet ports and on SFP module ports.

TDR can detect these cabling problems:

  • Open, broken, or cut twisted-pair wires—The wires are not connected to the wires from the remote device.
  • Shorted twisted-pair wires—The wires are touching each other or the wires from the remote device. For example, a shorted twisted pair can occur if one wire of the twisted pair is soldered to the other wire.

If one of the twisted-pair wires is open, TDR can find the length at which the wire is open.

Use TDR to diagnose and resolve cabling problems in these situations:

  • Replacing a switch
  • Setting up a wiring closet
  • Troubleshooting a connection between two devices when a link cannot be established or when it is not operating properly

When you run TDR, the switch reports accurate information in these situations:

  • The cable for the gigabit link is a solid-core cable.
  • The open-ended cable is not terminated.

When you run TDR, the switch does not report accurate information in these situations:

  • The cable for the gigabit link is a twisted-pair cable or is in series with a solid-core cable.
  • The link is a 10-megabit or a 100-megabit link.
  • The cable is a stranded cable.
  • The link partner is a Cisco IP Phone.
  • The link partner is not IEEE 802.3 compliant.

Debug Commands


Caution


Because debugging output is assigned high priority in the CPU process, it can render the system unusable. For this reason, use debug commands only to troubleshoot specific problems or during troubleshooting sessions with Cisco technical support staff. It is best to use debug commands during periods of lower network traffic and fewer users. Debugging during these periods decreases the likelihood that increased debug command processing overhead will affect system use.


All debug commands are entered in privileged EXEC mode, and most debug commands take no arguments.

For example, beginning in privileged EXEC mode, enter this command to enable the debugging for Switched Port Analyzer (SPAN):
Switch# debug span-session

The switch continues to generate output until you enter the no form of the command.

If you enable a debug command and no output appears, consider these possibilities:
  • The switch might not be properly configured to generate the type of traffic you want to monitor. Use the show running-config command to check its configuration.
  • Even if the switch is properly configured, it might not generate the type of traffic you want to monitor during the particular period that debugging is enabled. Depending on the feature you are debugging, you can use commands such as the TCP/IP ping command to generate network traffic.
To disable debugging of SPAN, enter this command in privileged EXEC mode:
Switch# no debug span-session
Alternately, in privileged EXEC mode, you can enter the undebug form of the command:
Switch# undebug span-session
To display the state of each debugging option, enter this command in privileged EXEC mode:
Switch# show debugging

Crashinfo Files

The crashinfo files save information that helps Cisco technical support representatives to debug problems that caused the Cisco IOS image to fail (crash). The switch generates two files at the time of the failure: full core and crashinfo.

The information in the crashinfo file includes the Cisco IOS image name and version that failed, a list of the processor registers, and a stack trace. You can provide this information to the Cisco technical support representative by using the show tech-support privileged EXEC command.

The switch writes the crash information to the console at the time of the failure. The switch creates two types of crashinfo files:
  • Basic crashinfo file—The switch automatically creates this file the next time you boot up the Cisco IOS image after the failure.
  • Extended crashinfo file—The switch automatically creates this file when the system is failing.
The file names have the following format:
 [fullcore | crashinfo]_[process that crashed]_[date]-[timestamp]-UTC
From IOS, you can view the crashinfo files on each switch by using the following command:

Switch#  dir crashinfo?
crashinfo-1: crashinfo-2: crashinfo-3: crashinfo:
Switch#

For example, to access the crashinfo directory for switch 1, enter
Switch dir crashinfo-1
From the ROMMON prompt, you can view the crashinfo files by using the dir command:
Switch: dir sda1
The following is sample output of a crashinfo file

Switch# dir crashinfo:

Directory of crashinfo:/

   12  -rwx        2768  Dec 31 1969 16:00:15 -08:00  koops.dat
   15  -rwx           0  Jan 12 2000 22:53:40 -08:00  deleted_crash_files
   16  -rwx     4246576  Jan 12 2000 22:53:40 -08:00  crashinfo_stack-mgr_20000113-065250-UTC
   17  -rwx          50   Oct 2 2012 03:18:42 -08:00  last_crashinfo
   26  -rwx          39  Jan 22 2013 14:14:14 -08:00  last_systemreport
   18  -rwx     2866565  Jan 12 2000 22:53:41 -08:00  fullcore_stack-mgr_20000113-065250-UTC
   20  -rwx     4391796   Feb 1 2000 17:50:44 -08:00  crashinfo_stack-mgr_20000202-014954-UTC
   21  -rwx     2920325   Feb 1 2000 17:50:45 -08:00  fullcore_stack-mgr_20000202-014954-UTC
34817  -rw-     1050209  Jan 10 2013 20:26:23 -08:00  system-report_1_20130111-042535-UTC.gz
18434  -rw-     1016913  Jan 11 2013 10:35:28 -08:00  system-report_1_20130111-183440-UTC.gz
18435  -rw-     1136167  Jan 22 2013 14:14:11 -08:00  system-report_1_20130122-221322-UTC.gz
34821  -rw-     1094631   Jan 2 2013 17:59:23 -08:00  system-report_1_20130103-015835-UTC.gz
 6147  -rw-      967429   Jan 3 2013 10:32:44 -08:00  system-report_1_20130103-183156-UTC.gz
34824  -rwx          50  Jan 22 2013 14:14:14 -08:00  deleted_sysreport_files
6155  -rwx         373  Jan 22 2013 14:14:13 -08:00  last_systemreport_log

145898496 bytes total (18569216 bytes free)
stack3#

The file name of the most recent crashinfo file is stored in last_crashinfo.
The file name of the most recent system report is stored in last_systemreport.

 
Switch#  
 

Basic crashinfo Files

The information in the basic file includes the Cisco IOS image name and version that failed, a list of the processor registers, and a stack trace. You can provide this information to the Cisco technical support representative by using the show tech-support privileged EXEC command.

Basic crashinfo files are kept in this directory on the flash file system:

flash:/crashinfo/.

The filenames are crashinfo_n where n is a sequence number.

Each new crashinfo file that is created uses a sequence number that is larger than any previously existing sequence number, so the file with the largest sequence number describes the most recent failure. Version numbers are used instead of a timestamp because the switches do not include a real-time clock. You cannot change the name of the file that the system will use when it creates the file. However, after the file is created, you can use the rename privileged EXEC command to rename it, but the contents of the renamed file will not be displayed by the show stacks or the show tech-support privileged EXEC command. You can delete crashinfo files by using the delete privileged EXEC command.

You can display the most recent basic crashinfo file (that is, the file with the highest sequence number at the end of its filename) by entering the show stacks or the show tech-support privileged EXEC command. You also can access the file by using any command that can copy or display files, such as the more or the copy privileged EXEC command.

Extended crashinfo Files

The switch creates the extended crashinfo file when the system is failing. The information in the extended file includes additional information that can help determine the cause of the switch failure. You provide this information to the Cisco technical support representative by manually accessing the file and using the more or the copy privileged EXEC command.

Extended crashinfo files are kept in this directory on the flash file system:

flash:/crashinfo_ext/.

The filenames are crashinfo_ext_n where n is a sequence number.

You can configure the switch to not create the extended creashinfo file by using the no exception crashinfo global configuration command.

Memory Consistency Check Routines

The switch runs memory consistency check routines to detect and correct invalid ternary content addressable memory (TCAM) table entries that can affect the performance of the switch.

If the switch cannot fix the error, it logs a system error message, specifying the TCAM space in which the error is located:
  • Unassigned space: Unassigned TCAM table entries for the current SDM template.
  • Hulc Forwarding TCAM Manager (HFTM) space: Related to the Layer 2 and Layer 3 forwarding tables.
  • Hulc Quality of Service (QoS)/access control list (ACL) TCAM Manager (HQATM) space: Related to ACL and ACL-like tables such as QoS classification and policy routing.

The output from the show platform tcam errors privileged EXEC command provides information about the TCAM memory consistency integrity on the switch.

Beginning in privileged EXEC mode, use the show platform tcam errors command to display the TCAM memory consistency check errors detected on the switch:

Command

Purpose

show platform tcam errors

Displays TCAM memory consistency check errors in the HQATM HFTM, and unassigned spaces on the TCAM.

This example shows the output of the show platform tcam errors command:
DomainMember# show platform tcam errors
TCAM Memory Consistency Checker Errors
--------------------------------------
TCAM Space Values Masks Fixups Retries Failures
Unassigned			0 				0 					0 					0 				0
HFTM 								0 				0 					0 					0 				0
HQATM 							0 				0 					0 					0 				0

DomainMember#
Table 1 Definitions of Fields in TCAM Checker Output

Column

Description

Values

The number of invalid values found in the TCAM tables.

Masks

The number of invalid masks found in the TCAM tables.

Fixups

The number of initial attempts to fix the invalid values or masks.

Retries

The number of attempts to fix the invalid values or masks.

Failures

The number of failed attempts to fix the invalid values or masks.

For more information about the show platform tcam errors privileged EXEC command, see the command reference for this release.

Onboard Failure Logging on the Switch

You can use the onboard failure logging (OBFL) feature to collect information about the switch. The information includes uptime, temperature, and voltage information and helps Cisco technical support representatives to troubleshoot switch problems. We recommend that you keep OBFL enabled and do not erase the data stored in the flash memory.

By default, OBFL is enabled. It collects information about the switch and small form-factor pluggable (SFP) modules. The switch stores this information in the flash memory:

  • CLI commands—Record of the OBFL CLI commands that are entered on a standalone switch or a switch stack member.
  • Environment data—Unique device identifier (UDI) information for a standalone switch or a stack member and for all the connected FRU devices: the product identification (PID), the version identification (VID), and the serial number.
  • Message—Record of the hardware-related system messages generated by a standalone switch or a stack member.
  • Power over Ethernet (PoE)—Record of the power consumption of PoE ports on a standalone switch or a stack member.
  • Temperature—Temperature of a standalone switch or a stack member.
  • Uptime data—Time when a standalone switch or a stack member starts, the reason the switch restarts, and the length of time the switch has been running since it last restarted.
  • Voltage—System voltages of a standalone switch or a stack member.

You should manually set the system clock or configure it by using Network Time Protocol (NTP).

When the switch is running, you can retrieve the OBFL data by using the show logging onboard privileged EXEC commands. If the switch fails, contact your Cisco technical support representative to find out how to retrieve the data.

When an OBFL-enabled switch is restarted, there is a 10-minute delay before logging of new data begins.

Troubleshooting CPU Utilization

This section lists some possible symptoms that could be caused by the CPU being too busy and shows how to verify a CPU utilization problem.

Possible Symptoms of High CPU Utilization

Excessive CPU utilization might result in these symptoms, but the symptoms might also result from other causes:

  • Spanning tree topology changes
  • EtherChannel links brought down due to loss of communication
  • Failure to respond to management requests (ICMP ping, SNMP timeouts, slow Telnet or SSH sessions)
  • UDLD flapping
  • IP SLAs failures because of SLAs responses beyond an acceptable threshold
  • DHCP or IEEE 802.1x failures if the switch does not forward or respond to requests

How to Troubleshoot the Software Configuration

Recovering from a Software Failure

Before You Begin

This recovery procedure requires that you have physical access to the switch.

This procedure uses boot loader commands and TFTP to recover from a corrupted or incorrect image file.


    Step 1   From your PC, download the software image file (image.bin) from Cisco.com.
    Step 2   Load the software image to your TFTP server.
    Step 3   Connect your PC to the switch Ethernet management port.
    Step 4   Unplug the switch power cord.
    Step 5   Press the Mode button, and at the same time, reconnect the power cord to the switch.
    Step 6   From the bootloader (ROMMON) prompt, ensure that you can ping your TFTP server.
    1. Set the IP address switch: set IP_ADDR ip_address subnet_mask

      Example:
      switch: set IP_ADDR 192.0.2.123/255.255.255.0
      
      
    2. Set the default router IP address switch: set DEFAULT_ROUTER ip_address

      Example:
      switch: set DEFAULT_ROUTER 192.0.2.1
      
      
    3. Verify that you can ping the TFTP server switch: ping ip_address_of_TFTP_server


    Example:
    switch: ping 192.0.2.15 
    ping 192.0.2.1 with 32 bytes of data...
    Host 192.0.2.1 is alive.
    switch:
    
    
    Step 7   Verify that you have a recovery image in your recovery partition (sda9:).

    This recovery image is required for recovery using the emergency-install feature.



    Example:
    switch: dir sda9:
    Directory of sda9:/
    
        2  drwx  1024       .
        2  drwx  1024       ..
       11  -rw-  18923068   c3850-recovery.bin
    
    36939776 bytes available (20830208 bytes used)
    switch:
    
    
    Step 8   From the bootloader (ROMMON) prompt, initiate the emergency-install feature that assists you in recovering the software image on your switch.

    WARNING: The emergency install command will erase your entire boot flash!



    Example:

    Recovering from a Lost or Forgotten Password

    The default configuration for the switch allows an end user with physical access to the switch to recover from a lost password by interrupting the boot process during power-on and by entering a new password. These recovery procedures require that you have physical access to the switch.


    Note


    On these switches, a system administrator can disable some of the functionality of this feature by allowing an end user to reset a password only by agreeing to return to the default configuration. If you are an end user trying to reset a password when password recovery has been disabled, a status message shows this during the recovery process.


    SUMMARY STEPS

      1.    Connect a terminal or PC to the switch.

      2.    Set the line speed on the emulation software to 9600 baud.

      3.    Power off the standalone switch or the entire switch stack.

      4.    Reconnect the power cord to the or the stack master. Within 15 seconds, press the Mode button while the System LED is still flashing green. Continue pressing the Mode button until all the system LEDs turn on and remain solid; then release the Mode button.

      5.    After recovering the password, reload the switch or the stack master .

      6.    Power on the remaining switches in the stack.


    DETAILED STEPS
      Step 1   Connect a terminal or PC to the switch.
      • Connect a terminal or a PC with terminal-emulation software to the switch console port. If you are recovering the password for a switch stack, connect to the console port of the stack master or
      • Connect a PC to the Ethernet management port. If you are recovering the password for a switch stack, connect to the Ethernet management port of a stack member .
      Step 2   Set the line speed on the emulation software to 9600 baud.
      Step 3   Power off the standalone switch or the entire switch stack.
      Step 4   Reconnect the power cord to the or the stack master. Within 15 seconds, press the Mode button while the System LED is still flashing green. Continue pressing the Mode button until all the system LEDs turn on and remain solid; then release the Mode button.
      • 
        Switch:
        Xmodem file system is available.
        Base ethernet MAC Address: 20:37:06:4d:e9:80
        Verifying bootloader digital signature.
        
        
        The system has been interrupted prior to loading the operating
        system software, console will be reset to 9600 baud rate.
        
        
        
        proceed to the Procedure with Password Recovery Enabled section, and follow the steps.
      Step 5   After recovering the password, reload the switch or the stack master .

      On a switch:

      Switch> reload
      Proceed with reload? [confirm] y
      
      

      On the active switch:

      Switch> reload slot <stack-active-member-number>
      Proceed with reload? [confirm] y
      
      
      Step 6   Power on the remaining switches in the stack.

      Procedure with Password Recovery Enabled

      If the password-recovery operation is enabled, this message appears:


        Step 1   Ignore the startup configuration with the following command:
        Switch: SWITCH_IGNORE_STARTUP_CFG=1
        
        
        Step 2   Boot the switch with the packages.conf file from flash.
        Switch: boot flash:packages.conf
        
        
        Step 3   Terminate the initial configuration dialog by answering No.
        Would you like to enter the initial configuration dialog? [yes/no]: No
        
        
        Step 4   At the switch prompt, enter privileged EXEC mode.
        Switch> enable      
        Switch#  
        
        
        Step 5   Copy the startup configuration to running configuration.
        Switch# copy startup-config running-config Destination filename [running-config]?
        
        

        Press Return in response to the confirmation prompts. The configuration file is now reloaded, and you can change the password.

        Step 6   Enter global configuration mode and change the enable password.
        Switch# configure terminal
        Switch(config)# 
        
        
        Step 7   Write the running configuration to the startup configuration file.
        Switch# copy running-config startup-config     
        
        
        Step 8   Confirm that manual boot mode is enabled.
        Switch# show boot
         
         BOOT variable = flash:packages.conf;
         Manual Boot = yes
         Enable Break = yes
        
        
        Step 9   Reload the switch.
        Switch# reload
        
        
        Step 10   Return the Bootloader parameters (previously changed in Steps 2 and 3) to their original values.
          
        Switch: switch: SWITCH_IGNORE_STARTUP_CFG=0
        
        
        Step 11   Boot the switch with the packages.conf file from flash.
        Switch: boot flash:packages.conf
        
        
        Step 12   After the switch boots up, disable manual boot on the switch.
        Switch(config)# no boot manual
        
        

        Procedure with Password Recovery Disabled

        If the password-recovery mechanism is disabled, this message appears:

        The password-recovery mechanism has been triggered, but
        is currently disabled.  Access to the boot loader prompt
        through the password-recovery mechanism is disallowed at
        this point.  However, if you agree to let the system be
        reset back to the default system configuration, access
        to the boot loader prompt can still be allowed.
        
        Would you like to reset the system back to the default configuration (y/n)?
        
        

        Caution


        Returning the switch to the default configuration results in the loss of all existing configurations. We recommend that you contact your system administrator to verify if there are backup switch and VLAN configuration files.


        • If you enter n (no), the normal boot process continues as if the Mode button had not been pressed; you cannot access the boot loader prompt, and you cannot enter a new password. You see the message:
          Press Enter to continue........
          
          
        • If you enter y (yes), the configuration file in flash memory and the VLAN database file are deleted. When the default configuration loads, you can reset the password.

          Step 1   Choose to continue with password recovery and delete the existing configuration:
          Would you like to reset the system back to the default configuration (y/n)? Y 
          
          
          Step 2   Display the contents of flash memory:
          Switch: dir flash:
          
          
          

          The switch file system appears.

          Step 3   Boot up the system:
          Switch: boot
          
          

          You are prompted to start the setup program. To continue with password recovery, enter N at the prompt:

          Continue with the configuration dialog? [yes/no]: N
          
          
          Step 4   At the switch prompt, enter privileged EXEC mode:
          Switch> enable
          
          
          Step 5   Enter global configuration mode:
          Switch# configure terminal
          
          
          Step 6   Change the password:
          Switch(config)# enable secret password
          
          

          The secret password can be from 1 to 25 alphanumeric characters, can start with a number, is case sensitive, and allows spaces but ignores leading spaces.

          Step 7   Return to privileged EXEC mode:
          Switch(config)# exit
          Switch# 
          
          
          Note   

          Before continuing to Step 9, power on any connected stack members and wait until they have completely initialized.

          Step 8   Write the running configuration to the startup configuration file:
          Switch# copy running-config startup-config
          
          

          The new password is now in the startup configuration.

          Step 9   You must now reconfigure the switch. If the system administrator has the backup switch and VLAN configuration files available, you should use those.

          Recovering from a Command Switch Failure

          This section describes how to recover from a failed command switch. You can configure a redundant command switch group by using the Hot Standby Router Protocol (HSRP).

          Note


          HSRP is the preferred method for supplying redundancy to a cluster.

          If you have not configured a standby command switch, and your command switch loses power or fails in some other way, management contact with the member switches is lost, and you must install a new command switch. However, connectivity between switches that are still connected is not affected, and the member switches forward packets as usual. You can manage the members as standalone switches through the console port, or, if they have IP addresses, through the other management interfaces.

          You can prepare for a command switch failure by assigning an IP address to a member switch or another switch that is command-capable, making a note of the command-switch password, and cabling your cluster to provide redundant connectivity between the member switches and the replacement command switch. These sections describe two solutions for replacing a failed command switch:
          • Replacing a Failed Command Switch with a Cluster Member
          • Replacing a Failed Command Switch with Another Switch

          These recovery procedures require that you have physical access to the switch.

          For information on command-capable switches, see the release notes.

          Replacing a Failed Command Switch with a Cluster Member

          To replace a failed command switch with a command-capable member in the same cluster, follow these steps:

          SUMMARY STEPS

            1.    Disconnect the command switch from the member switches, and physically remove it from the cluster.

            2.    Insert the member switch in place of the failed command switch, and duplicate its connections to the cluster members.

            3.    Start a CLI session on the new command switch.

            4.    At the switch prompt, enter privileged EXEC mode:

            5.    Enter the password of the failed command switch.

            6.    Enter global configuration mode.

            7.    Remove the member switch from the cluster.

            8.    Return to privileged EXEC mode.

            9.    Use the setup program to configure the switch IP information. This program prompts you for IP address information and passwords. From privileged EXEC mode, enter setup, and press Return.

            10.    Enter Y at the first prompt.

            11.    Respond to the questions in the setup program.

            12.    When prompted for the enable secret and enable passwords, enter the passwords of the failed command switch again.

            13.    When prompted, make sure to enable the switch as the cluster command switch, and press Return.

            14.    When prompted, assign a name to the cluster, and press Return.

            15.    After the initial configuration displays, verify that the addresses are correct.

            16.    If the displayed information is correct, enter Y, and press Return.

            17.    Start your browser, and enter the IP address of the new command switch.

            18.    From the Cluster menu, select Add to Cluster to display a list of candidate switches to add to the cluster.


          DETAILED STEPS
             Command or ActionPurpose
            Step 1Disconnect the command switch from the member switches, and physically remove it from the cluster.    
            Step 2Insert the member switch in place of the failed command switch, and duplicate its connections to the cluster members.    
            Step 3Start a CLI session on the new command switch.   You can access the CLI by using the console port or, if an IP address has been assigned to the switch, by using Telnet. For details about using the console port, see the switch hardware installation guide.  
            Step 4At the switch prompt, enter privileged EXEC mode:  
            Switch> enable
            Switch#
             
            Step 5Enter the password of the failed command switch.    
            Step 6Enter global configuration mode.  
            Switch# configure terminal
            Enter configuration commands, one per line. End with CNTL/Z.
             
            Step 7Remove the member switch from the cluster.  
            Switch(config)# no cluster commander-address
             
            Step 8Return to privileged EXEC mode.  
            Switch(config)# end
            Switch#
             
            Step 9Use the setup program to configure the switch IP information. This program prompts you for IP address information and passwords. From privileged EXEC mode, enter setup, and press Return.  
            Switch# setup
            --- System Configuration Dialog ---
            Continue with configuration dialog? [yes/no]: y
            
            At any point you may enter a question mark '?' for help.
            Use ctrl-c to abort configuration dialog at any prompt.
            Default settings are in square brackets '[]'.
            
            Basic management setup configures only enough connectivity
            for management of the system, extended setup will ask you
            to configure each interface on the system
            
            Would you like to enter basic management setup? [yes/no]:
             
            Step 10Enter Y at the first prompt.   The prompts in the setup program vary depending on the member switch that you selected to be the command switch:
            Continue with configuration dialog? [yes/no]: y
            or
            Configuring global parameters:
            If this prompt does not appear, enter enable, and press Return. Enter setup, and press Return to start the setup program.  
            Step 11Respond to the questions in the setup program.   When prompted for the hostname, recall that on a command switch, the hostname is limited to 28 characters; on a member switch to 31 characters. Do not use -n, where n is a number, as the last characters in a hostname for any switch. When prompted for the Telnet (virtual terminal) password, recall that it can be from 1 to 25 alphanumeric characters, is case sensitive, allows spaces, but ignores leading spaces.  
            Step 12When prompted for the enable secret and enable passwords, enter the passwords of the failed command switch again.    
            Step 13When prompted, make sure to enable the switch as the cluster command switch, and press Return.    
            Step 14When prompted, assign a name to the cluster, and press Return.   The cluster name can be 1 to 31 alphanumeric characters, dashes, or underscores.  
            Step 15After the initial configuration displays, verify that the addresses are correct.    
            Step 16If the displayed information is correct, enter Y, and press Return.   If this information is not correct, enter N, press Return, and begin again at Step 9.  
            Step 17Start your browser, and enter the IP address of the new command switch.    
            Step 18From the Cluster menu, select Add to Cluster to display a list of candidate switches to add to the cluster.    

            Replacing a Failed Command Switch with Another Switch

            To replace a failed command switch with a switch that is command-capable but not part of the cluster, follow these steps:

            SUMMARY STEPS

              1.    Insert the new switch in place of the failed command switch, and duplicate its connections to the cluster members.

              2.    Start a CLI session on the new command switch.

              3.    At the switch prompt, enter privileged EXEC mode:

              4.    Enter the password of the failed command switch.

              5.    Use the setup program to configure the switch IP information.

              6.    Enter Y at the first prompt.

              7.    Respond to the questions in the setup program.

              8.    When prompted for the enable secret and enable passwords, enter the passwords of the failed command switch again.

              9.    When prompted, make sure to enable the switch as the cluster command switch, and press Return.

              10.    When prompted, assign a name to the cluster, and press Return.

              11.    When the initial configuration displays, verify that the addresses are correct.

              12.    If the displayed information is correct, enter Y, and press Return.

              13.    Start your browser, and enter the IP address of the new command switch.

              14.    From the Cluster menu, select Add to Cluster to display a list of candidate switches to add to the cluster.


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 Insert the new switch in place of the failed command switch, and duplicate its connections to the cluster members.  

               

              Step 2Start a CLI session on the new command switch.   You can access the CLI by using the console port or, if an IP address has been assigned to the switch, by using Telnet. For details about using the console port, see the switch hardware installation guide.  
              Step 3At the switch prompt, enter privileged EXEC mode:  
              Switch> enable
              Switch#
               
              Step 4Enter the password of the failed command switch.    
              Step 5Use the setup program to configure the switch IP information.   This program prompts you for IP address information and passwords. From privileged EXEC mode, enter setup, and press Return.
              Switch# setup
              --- System Configuration Dialog ---
              Continue with configuration dialog? [yes/no]: y
              
              At any point you may enter a question mark '?' for help.
              Use ctrl-c to abort configuration dialog at any prompt.
              Default settings are in square brackets '[]'.
              
              Basic management setup configures only enough connectivity
              for management of the system, extended setup will ask you
              to configure each interface on the system
              
              Would you like to enter basic management setup? [yes/no]:
               
              Step 6Enter Y at the first prompt.   The prompts in the setup program vary depending on the switch you selected to be the command switch:
              Continue with configuration dialog? [yes/no]: y
              or
              Configuring global parameters:
              If this prompt does not appear, enter enable, and press Return. Enter setup, and press Return to start the setup program.  
              Step 7Respond to the questions in the setup program.   When prompted for the hostname, recall that on a command switch, the hostname is limited to 28 characters. Do not use -n, where n is a number, as the last character in a hostname for any switch. When prompted for the Telnet (virtual terminal) password, recall that it can be from 1 to 25 alphanumeric characters, is case sensitive, allows spaces, but ignores leading spaces.  
              Step 8When prompted for the enable secret and enable passwords, enter the passwords of the failed command switch again.    
              Step 9When prompted, make sure to enable the switch as the cluster command switch, and press Return.    
              Step 10When prompted, assign a name to the cluster, and press Return.   The cluster name can be 1 to 31 alphanumeric characters, dashes, or underscores.  
              Step 11When the initial configuration displays, verify that the addresses are correct.    
              Step 12If the displayed information is correct, enter Y, and press Return.   If this information is not correct, enter N, press Return, and begin again at Step 9.  
              Step 13Start your browser, and enter the IP address of the new command switch.    
              Step 14From the Cluster menu, select Add to Cluster to display a list of candidate switches to add to the cluster.    

              Recovering from Lost Cluster Member Connectivity

              Some configurations can prevent the command switch from maintaining contact with member switches. If you are unable to maintain management contact with a member, and the member switch is forwarding packets normally, check for these conflicts:
              • A member switch (Catalyst 3750, Catalyst 3560, Catalyst 3550, Catalyst 3500 XL, Catalyst 2970, Catalyst 2960, Catalyst 2950, Catalyst 2900 XL, Catalyst 2820, and Catalyst 1900 switch) cannot connect to the command switch through a port that is defined as a network port.
              • Catalyst 3500 XL, Catalyst 2900 XL, Catalyst 2820, and Catalyst 1900 member switches must connect to the command switch through a port that belongs to the same management VLAN.
              • A member switch (Catalyst 3750, Catalyst 3560, Catalyst 3550, Catalyst 2970, Catalyst 2960, Catalyst 2950, Catalyst 3500 XL, Catalyst 2900 XL, Catalyst 2820, and Catalyst 1900 switch) connected to the command switch through a secured port can lose connectivity if the port is disabled because of a security violation.

              Preventing Autonegotiation Mismatches

              The IEEE 802.3ab autonegotiation protocol manages the switch settings for speed (10 Mb/s, 100 Mb/s, and 1000 Mb/s, excluding SFP module ports) and duplex (half or full). There are situations when this protocol can incorrectly align these settings, reducing performance. A mismatch occurs under these circumstances:

              • A manually set speed or duplex parameter is different from the manually set speed or duplex parameter on the connected port.
              • A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.

              To maximize switch performance and ensure a link, follow one of these guidelines when changing the settings for duplex and speed:

              • Let both ports autonegotiate both speed and duplex.
              • Manually set the speed and duplex parameters for the ports on both ends of the connection.

              Note


              If a remote device does not autonegotiate, configure the duplex settings on the two ports to match. The speed parameter can adjust itself even if the connected port does not autonegotiate.


              Troubleshooting SFP Module Security and Identification

              Cisco small form-factor pluggable (SFP) modules have a serial EEPROM that contains the module serial number, the vendor name and ID, a unique security code, and cyclic redundancy check (CRC). When an SFP module is inserted in the switch, the switch software reads the EEPROM to verify the serial number, vendor name and vendor ID, and recompute the security code and CRC. If the serial number, the vendor name or vendor ID, the security code, or CRC is invalid, the software generates a security error message and places the interface in an error-disabled state.


              Note


              The security error message references the GBIC_SECURITY facility. The switch supports SFP modules and does not support GBIC modules. Although the error message text refers to GBIC interfaces and modules, the security messages actually refer to the SFP modules and module interfaces.


              If you are using a non-Cisco SFP module, remove the SFP module from the switch, and replace it with a Cisco module. After inserting a Cisco SFP module, use the errdisable recovery cause gbic-invalid global configuration command to verify the port status, and enter a time interval for recovering from the error-disabled state. After the elapsed interval, the switch brings the interface out of the error-disabled state and retries the operation.

              If the module is identified as a Cisco SFP module, but the system is unable to read vendor-data information to verify its accuracy, an SFP module error message is generated. In this case, you should remove and reinsert the SFP module. If it continues to fail, the SFP module might be defective.

              Monitoring SFP Module Status

              You can check the physical or operational status of an SFP module by using the show interfaces transceiver privileged EXEC command. This command shows the operational status, such as the temperature and the current for an SFP module on a specific interface and the alarm status. You can also use the command to check the speed and the duplex settings on an SFP module.

              Executing Ping

              If you attempt to ping a host in a different IP subnetwork, you must define a static route to the network or have IP routing configured to route between those subnets.

              IP routing is disabled by default on all switches.


              Note


              Though other protocol keywords are available with the ping command, they are not supported in this release.


              Use this command to ping another device on the network from the switch:

              Command

              Purpose

              ping ip host | address

              Switch# ping 172.20.52.3
              
              

              Pings a remote host through IP or by supplying the hostname or network address.

              Monitoring the Physical Path

              You can monitor the physical path that a packet takes from a source device to a destination device by using one of these privileged EXEC commands:

              Table 2 Monitoring the Physical Path
              Command Purpose

              tracetroute mac [interface interface-id] {source-mac-address} [interface interface-id] {destination-mac-address} [vlan vlan-id] [detail]

              Displays the Layer 2 path taken by the packets from the specified source MAC address to the specified destination MAC address.

              tracetroute mac ip {source-ip-address | source-hostname}{destination-ip-address | destination-hostname} [detail]

              Displays the Layer 2 path taken by the packets from the specified source IP address or hostname to the specified destination IP address or hostname.

              Executing IP Traceroute


              Note


              Though other protocol keywords are available with the traceroute privileged EXEC command, they are not supported in this release.


              Command

              Purpose

              traceroute ip host

              Switch# traceroute ip 192.51.100.1
              
              

              Traces the path that packets take through the network.

              Running TDR and Displaying the Results

              To run TDR, enter the test cable-diagnostics tdr interface interface-id privileged EXEC command.

              To display the results, enter the show cable-diagnostics tdr interface interface-id privileged EXEC command.

              Redirecting Debug and Error Message Output

              By default, the network server sends the output from debug commands and system error messages to the console. If you use this default, you can use a virtual terminal connection to monitor debug output instead of connecting to the console port or the Ethernet management port.

              Possible destinations include the console, virtual terminals, internal buffer, and UNIX hosts running a syslog server. The syslog format is compatible with 4.3 Berkeley Standard Distribution (BSD) UNIX and its derivatives.


              Note


              Be aware that the debugging destination you use affects system overhead. When you log messages to the console, very high overhead occurs. When you log messages to a virtual terminal, less overhead occurs. Logging messages to a syslog server produces even less, and logging to an internal buffer produces the least overhead of any method.


              Using the show platform forward Command

              The output from the show platform forward privileged EXEC command provides some useful information about the forwarding results if a packet entering an interface is sent through the system. Depending upon the parameters entered about the packet, the output provides lookup table results and port maps used to calculate forwarding destinations, bitmaps, and egress information.


              Note


              For more syntax and usage information for the show platform forward command, see the switch command reference for this release.

              Most of the information in the output from the command is useful mainly for technical support personnel, who have access to detailed information about the switch application-specific integrated circuits (ASICs). However, packet forwarding information can also be helpful in troubleshooting.

              Example: Verifying the Problem and Cause for High CPU Utilization

              To determine if high CPU utilization is a problem, enter the show processes cpu sorted privileged EXEC command. Note the underlined information in the first line of the output example.

              Switch# show processes cpu sorted
              CPU utilization for five seconds: 8%/0%; one minute: 7%; five minutes: 8%
              PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process 
              309 42289103 752750 56180 1.75% 1.20% 1.22% 0 RIP Timers 
              140 8820183 4942081 1784 0.63% 0.37% 0.30% 0 HRPC qos request 
              100 3427318 16150534 212 0.47% 0.14% 0.11% 0 HRPC pm-counters 
              192 3093252 14081112 219 0.31% 0.14% 0.11% 0 Spanning Tree 
              143 8 37 216 0.15% 0.01% 0.00% 0 Exec 
              ...
              <output truncated>
              
              

              This example shows normal CPU utilization. The output shows that utilization for the last 5 seconds is 8%/0%, which has this meaning:

              • The total CPU utilization is 8 percent, including both time running Cisco IOS processes and time spent handling interrupts.
              • The time spent handling interrupts is zero percent.
              Table 3 Troubleshooting CPU Utilization Problems

              Type of Problem

              Cause

              Corrective Action

              Interrupt percentage value is almost as high as total CPU utilization value.

              The CPU is receiving too many packets from the network.

              Determine the source of the network packet. Stop the flow, or change the switch configuration. See the section on “Analyzing Network Traffic.”

              Total CPU utilization is greater than 50% with minimal time spent on interrupts.

              One or more Cisco IOS process is consuming too much CPU time. This is usually triggered by an event that activated the process.

              Identify the unusual event, and troubleshoot the root cause. See the section on “Debugging Active Processes.”

              Scenarios to Troubleshoot Power over Ethernet (PoE)

              Table 4 Power over Ethernet Troubleshooting Scenarios

              Symptom or Problem

              Possible Cause and Solution

              Only one port does not have PoE.

              Trouble is on only one switch port. PoE and non-PoE devices do not work on this port, but do on other ports.

              Verify that the powered device works on another PoE port.

              Use the show run, or show interface status user EXEC commands to verify that the port is not shut down or error-disabled.

              Note   

              Most switches turn off port power when the port is shut down, even though the IEEE specifications make this optional.

              Verify that the Ethernet cable from the powered device to the switch port is good: Connect a known good non-PoE Ethernet device to the Ethernet cable, and make sure that the powered device establishes a link and exchanges traffic with another host.

              Verify that the total cable length from the switch front panel to the powered device is not more than 100 meters.

              Disconnect the Ethernet cable from the switch port. Use a short Ethernet cable to connect a known good Ethernet device directly to this port on the switch front panel (not on a patch panel). Verify that it can establish an Ethernet link and exchange traffic with another host, or ping the port VLAN SVI. Next, connect a powered device to this port, and verify that it powers on.

              If a powered device does not power on when connected with a patch cord to the switch port, compare the total number of connected powered devices to the switch power budget (available PoE). Use the show inline power command to verify the amount of available power.

              No PoE on all ports or a group of ports.

              Trouble is on all switch ports. Nonpowered Ethernet devices cannot establish an Ethernet link on any port, and PoE devices do not power on.

              If there is a continuous, intermittent, or reoccurring alarm related to power, replace the power supply if possible it is a field-replaceable unit. Otherwise, replace the switch.

              If the problem is on a consecutive group of ports but not all ports, the power supply is probably not defective, and the problem could be related to PoE regulators in the switch.

              Use the show log privileged EXEC command to review alarms or system messages that previously reported PoE conditions or status changes.

              If there are no alarms, use the show interface status command to verify that the ports are not shut down or error-disabled. If ports are error-disabled, use the shut and no shut interface configuration commands to reenable the ports.

              Use the show env power and show power inline privileged EXEC commands to review the PoE status and power budget (available PoE).

              Review the running configuration to verify that power inline never is not configured on the ports.

              Connect a nonpowered Ethernet device directly to a switch port. Use only a short patch cord. Do not use the existing distribution cables. Enter the shut and no shut interface configuration commands, and verify that an Ethernet link is established. If this connection is good, use a short patch cord to connect a powered device to this port and verify that it powers on. If the device powers on, verify that all intermediate patch panels are correctly connected.

              Disconnect all but one of the Ethernet cables from switch ports. Using a short patch cord, connect a powered device to only one PoE port. Verify the powered device does not require more power than can be delivered by the switch port.

              Use the show power inline privileged EXEC command to verify that the powered device can receive power when the port is not shut down. Alternatively, watch the powered device to verify that it powers on.

              If a powered device can power on when only one powered device is connected to the switch, enter the shut and no shut interface configuration commands on the remaining ports, and then reconnect the Ethernet cables one at a time to the switch PoE ports. Use the show interface status and show power inline privileged EXEC commands to monitor inline power statistics and port status.

              If there is still no PoE at any port, a fuse might be open in the PoE section of the power supply. This normally produces an alarm. Check the log again for alarms reported earlier by system messages.

              Cisco IP Phone disconnects or resets.

              After working normally, a Cisco phone or wireless access point intermittently reloads or disconnects from PoE.

              Verify all electrical connections from the switch to the powered device. Any unreliable connection results in power interruptions and irregular powered device functioning such as erratic powered device disconnects and reloads.

              Verify that the cable length is not more than 100 meters from the switch port to the powered device.

              Notice what changes in the electrical environment at the switch location or what happens at the powered device when the disconnect occurs.

              Notice whether any error messages appear at the same time a disconnect occurs. Use the show log privileged EXEC command to review error messages.

              Verify that an IP phone is not losing access to the Call Manager immediately before the reload occurs. (It might be a network problem and not a PoE problem.)

              Replace the powered device with a non-PoE device, and verify that the device works correctly. If a non-PoE device has link problems or a high error rate, the problem might be an unreliable cable connection between the switch port and the powered device.

              Non-Cisco powered device does not work on Cisco PoE switch.

              A non-Cisco powered device is connected to a Cisco PoE switch, but never powers on or powers on and then quickly powers off. Non-PoE devices work normally.

              Use the show power inline command to verify that the switch power budget (available PoE) is not depleted before or after the powered device is connected. Verify that sufficient power is available for the powered device type before you connect it.

              Use the show interface status command to verify that the switch detects the connected powered device.

              Use the show log command to review system messages that reported an overcurrent condition on the port. Identify the symptom precisely: Does the powered device initially power on, but then disconnect? If so, the problem might be an initial surge-in (or inrush) current that exceeds a current-limit threshold for the port.

              Configuration Examples for Troubleshooting Software

              Example: Pinging an IP Host

              This example shows how to ping an IP host:

              Switch# ping 172.20.52.3
              
              Type escape sequence to abort.
              Sending 5, 100-byte ICMP Echoes to 172.20.52.3, timeout is 2 seconds:
              !!!!!
              Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
              Switch#
              
              Table 5 Ping Output Display Characters

              Character

              Description

              !

              Each exclamation point means receipt of a reply.

              .

              Each period means the network server timed out while waiting for a reply.

              U

              A destination unreachable error PDU was received.

              C

              A congestion experienced packet was received.

              I

              User interrupted test.

              ?

              Unknown packet type.

              &

              Packet lifetime exceeded.

              To end a ping session, enter the escape sequence (Ctrl-^ X by default). Simultaneously press and release the Ctrl, Shift, and 6 keys and then press the X key.

              Example: Performing a Traceroute to an IP Host

              This example shows how to perform a traceroute to an IP host:

              Switch# traceroute ip 192.0.2.10
              
              Type escape sequence to abort.
              Tracing the route to 192.0.2.10
              
                1 192.0.2.1 0 msec 0 msec 4 msec
                2 192.0.2.203 12 msec 8 msec 0 msec
                3 192.0.2.100 4 msec 0 msec 0 msec
                4 192.0.2.10 0 msec 4 msec 0 msec
                 
              
              

              The display shows the hop count, the IP address of the router, and the round-trip time in milliseconds for each of the three probes that are sent.

              Table 6 Traceroute Output Display Characters

              Character

              Description

              *

              The probe timed out.

              ?

              Unknown packet type.

              A

              Administratively unreachable. Usually, this output means that an access list is blocking traffic.

              H

              Host unreachable.

              N

              Network unreachable.

              P

              Protocol unreachable.

              Q

              Source quench.

              U

              Port unreachable.

              To end a trace in progress, enter the escape sequence (Ctrl-^ X by default). Simultaneously press and release the Ctrl, Shift, and 6 keys and then press the X key.

              Example: Enabling All System Diagnostics


              Caution


              Because debugging output takes priority over other network traffic, and because the debug all privileged EXEC command generates more output than any other debug command, it can severely diminish switch performance or even render it unusable. In virtually all cases, it is best to use more specific debug commands.


              This command disables all-system diagnostics:

              Switch# debug all
              
              

              The no debug all privileged EXEC command disables all diagnostic output. Using the no debug all command is a convenient way to ensure that you have not accidentally left any debug commands enabled.