Cisco ME3400 Ethernet Access Switch Software Configuration Guide, Rel 12.2(60)EZ
Troubleshooting
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Troubleshooting

Table Of Contents

Troubleshooting

Recovering from Corrupted Software By Using the Xmodem Protocol

Recovering from a Lost or Forgotten Password

Procedure with Password Recovery Enabled

Procedure with Password Recovery Disabled

Preventing Autonegotiation Mismatches

SFP Module Security and Identification

Monitoring SFP Module Status

Monitoring Temperature

Using Ping

Understanding Ping

Using Ping

All Software Versions

Metro IP Access Image

Ping Responses

Summary

Using Layer 2 Traceroute

Understanding Layer 2 Traceroute

Layer 2 Traceroute Usage Guidelines

Displaying the Physical Path

Using IP Traceroute

Understanding IP Traceroute

Executing IP Traceroute

Using TDR

Understanding TDR

Running TDR and Displaying the Results

Using Debug Commands

Enabling Debugging on a Specific Feature

Enabling All-System Diagnostics

Redirecting Debug and Error Message Output

Using the show platform forward Command

Using the crashinfo File


Troubleshooting


This chapter describes how to identify and resolve software problems related to the Cisco IOS software on the Cisco ME 3400 switch.

You can use the command-line interface (CLI) to identify and solve problems.

Additional troubleshooting information related to hardware is provided in the hardware installation guide.


Note For complete syntax and usage information for the commands used in this chapter, see the command reference for this release and the Cisco IOS Command Summary, Release 12.2.


Recovering from Corrupted Software By Using the Xmodem Protocol

Recovering from a Lost or Forgotten Password


Note Recovery procedures require that you have physical access to the switch.


Preventing Autonegotiation Mismatches

SFP Module Security and Identification

Monitoring SFP Module Status

Monitoring Temperature

Using Ping

Using Layer 2 Traceroute

Using IP Traceroute

Using TDR

Using Debug Commands

Using the show platform forward Command

Using the crashinfo File

Recovering from Corrupted Software By Using the Xmodem Protocol

Switch software can be corrupted during an upgrade, by downloading the wrong 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.

This procedure uses the Xmodem Protocol to recover from a corrupt or wrong image file. There are many software packages that support the Xmodem Protocol, and this procedure is largely dependent on the emulation software that you are using.

This recovery procedure requires that you have physical access to the switch. The Cisco ME switch boot loader uses break-key detection to stop the automatic boot sequence for the password recovery purpose.


Note The break key character is different for each operating system.

On a SUN work station running UNIX, Ctrl-C is the break key.

On a PC running Windows XP or 2000, Ctrl-Break is the break key.

Cisco TAC has tabulated break keys for most common operating systems and an alternative break key sequence for those terminal emulators that do not support the break keys. For that list, see
http://www.cisco.com/warp/public/701/61.html#how-to



Step 1 From your PC, download the software image tar file (image_filename.tar) from Cisco.com.

The Cisco IOS image is stored as a bin file in a directory in the tar file. For information about locating the software image files on Cisco.com, see the release notes

Step 2 Extract the bin file from the tar file.

If you are using Windows, use a zip program that can read a tar file. Use the zip program to navigate to and extract the bin file.

If you are using UNIX, follow these steps:

1. Display the contents of the tar file by using the tar -tvf <image_filename.tar> UNIX command.

switch% tar -tvf image_filename.tar
 
   

2. Locate the bin file, and extract it by using the tar -xvf <image_filename.tar> <image_filename.bin> UNIX command.

switch% tar -xvf image_filename.tar image_filename.bin
x image-name-mz.122-50.SE.bin 3970586 bytes, 7756 tape blocks
 
   

3. Verify that the bin file was extracted by using the ls -l <image_filename.bin> UNIX command.

switch% ls -l image_filename.bin
-rw-r--r--   1 boba      3560586 Apr 21 12:00
image-name-mz.122-50.SE.bin
 
   

Step 3 Connect your PC with terminal-emulation software supporting the Xmodem Protocol to the switch console port.

Step 4 Set the line speed on the emulation software to 9600 baud.

Step 5 Unplug the switch power cord.

Step 6 Press the break key, and at the same time, reconnect the power cord to the switch.

You can release the break key a second or two after the LED above port 1 goes off. Several lines of information about the software appear along with instructions:

The system has been interrupted, or encountered an error during initialization of the 
flash filesystem. The following commands will initialize the flash filesystem, and finish 
loading the operating system software:
 
   
flash_init
load_helper
boot
 
   

Step 7 Initialize the flash file system:

switch: flash_init
 
   

Step 8 If you had set the console port speed to anything other than 9600, it has been reset to that particular speed. Change the emulation software line speed to match that of the switch console port.

Step 9 Load any helper files:

switch: load_helper
 
   

Step 10 Start the file transfer by using the Xmodem Protocol.

switch: copy xmodem: flash:image_filename.bin
 
   

Step 11 After the Xmodem request appears, use the appropriate command on the terminal-emulation software to start the transfer and to copy the software image into flash memory.

Step 12 Boot the newly downloaded Cisco IOS image.

switch:boot flash:image_filename.bin
 
   

Step 13 Use the archive download-sw privileged EXEC command to download the software image to the switch.

Step 14 Use the reload privileged EXEC command to restart the switch and to verify that the new software image is operating properly.

Step 15 Delete the flash:image_filename.bin file from the switch.


Recovering from a Lost or Forgotten Password

The default configuration for the switch allows an end user to recover from a lost password by interrupting the boot process during power-on and by entering a new password.


Note On these switches, a system administrator can disable some of the functionality of password recovery 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.

Disabling password recovery provides configuration file security by preventing unauthorized users from accessing the configuration file.


The Cisco ME switch boot loader uses break-key detection to stop the automatic boot sequence for the password recovery purpose.


Note The break key character is different for each operating system.

On a SUN work station running UNIX, Ctrl-C is the break key.

On a PC running Windows XP or 2000, Ctrl-Break is the break key.

Cisco TAC has tabulated break keys for most common operating systems and an alternative break key sequence for those terminal emulators that do not support the break keys. To see that list go to:
http://www.cisco.com/warp/public/701/61.html#how-to


These sections describes how to recover a forgotten or lost switch password:

Procedure with Password Recovery Enabled

Procedure with Password Recovery Disabled

You enable or disable password recovery by using the service password-recovery global configuration command.

Follow the steps in this procedure if you have forgotten or lost the switch password.


Step 1 Connect a terminal or PC with terminal-emulation software to the switch console port.

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

Step 3 Power off the switch.

Reconnect the power cord to the switch.

Step 4 After the switch performs POST, the switch begins the autoboot process. The boot loader prompts the user for a break key character during the boot-up sequence, as shown in this example:

***** The system will autoboot in 5 seconds ***** 
 
   
Send a break key to prevent autobooting. 
 
   

You must enter the break key on the console terminal within 5 seconds of receiving the message that the system will autoboot. The System LED flashes green until the break key is accepted. After the break key is accepted, the System LED turns off until after the switch boots.

Several lines of information about the software appear with instructions, informing you if the password recovery procedure has been disabled or not.

If you see a message that begins with this:

The system has been interrupted, or encountered an error during initializion of the 
flash filesystem. The following commands will initialize the flash filesystem, and 
finish loading the operating system software:
 
   
flash_init
load_helper
boot
 
   

proceed to the "Procedure with Password Recovery Enabled" section, and follow the steps.

If you see a message that begins with this:

The password-recovery mechanism has been triggered, but is currently disabled. 
 
   

proceed to the "Procedure with Password Recovery Disabled" section, and follow the steps.

Step 5 After recovering the password, reload the switch:

Switch> reload 
Proceed with reload? [confirm] y
 
   

Procedure with Password Recovery Enabled

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

The system has been interrupted, or encountered an error during initializion of the flash 
filesystem. The following commands will initialize the flash filesystem, and finish 
loading the operating system software:
 
   
flash_init
load_helper
boot

Step 1 Initialize the flash file system:

switch: flash_init
 
   

Step 2 If you had set the console port speed to anything other than 9600, it has been reset to that particular speed. Change the emulation software line speed to match that of the switch console port.

Step 3 Load any helper files:

switch: load_helper
 
   

Step 4 Display the contents of flash memory:

switch: dir flash:
 
   

The switch file system appears:

Directory of flash:
   13  drwx         192   Mar 01 1993 22:30:48 image-name-mz.122-50-EX
   11  -rwx        5825   Mar 01 1993 22:31:59  config.text
   18  -rwx         720   Mar 01 1993 02:21:30  vlan.dat
 
   
16128000 bytes total (10003456 bytes free) 
 
   

Step 5 Rename the configuration file to config.text.old.

This file contains the password definition.

switch: rename flash:config.text flash:config.text.old
 
   

Step 6 Boot the system:

switch: boot
 
   

You are prompted to start the setup program. Enter N at the prompt:

Continue with the configuration dialog? [yes/no]: N
 
   

Step 7 At the switch prompt, enter privileged EXEC mode:

Switch> enable
 
   

Step 8 Rename the configuration file to its original name:

Switch# rename flash:config.text.old flash:config.text 
 
   

Step 9 Copy the configuration file into memory:

Switch# copy flash:config.text system:running-config 
Source filename [config.text]? 
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 10 Enter global configuration mode:

Switch# configure terminal
 
   

Step 11 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 12 Return to privileged EXEC mode:

Switch (config)# exit 
Switch# 
 
   

Step 13 Write the running configuration to the startup configuration file:

Switch# copy running-config startup-config
 
   

The new password is now in the startup configuration.


Note This procedure is likely to leave your switch virtual interface in a shutdown state. You can identify this interface by entering the show running-config privileged EXEC command. To re-enable the interface, enter the interface vlan vlan-id global configuration command, and specify the VLAN ID of the shutdown interface. With the switch in interface configuration mode, enter the no shutdown command.


Step 14 Reload the switch:

Switch# reload
 
   

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.


Note Disabling password recovery provides configuration file security by preventing unauthorized users from accessing the configuration file.


If you enter n (no), the normal boot process continues as if the break key 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 Elect to continue with password recovery and lose the existing configuration:

Would you like to reset the system back to the default configuration (y/n)? Y 
 
   

Step 2 Load any helper files:

Switch: load_helper
 
   

Step 3 Display the contents of flash memory:

switch: dir flash:
 
   

The switch file system appears:

Directory of flash:
13  drwx         192   Mar 01 1993 22:30:48 image-name-mz.122-50-SE
 
   
16128000 bytes total (10003456 bytes free) 
 
   

Step 4 Boot 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 5 At the switch prompt, enter privileged EXEC mode:

Switch> enable
 
   

Step 6 Enter global configuration mode:

Switch# configure terminal
 
   

Step 7 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 8 Return to privileged EXEC mode:

Switch (config)# exit 
Switch# 
 
   

Step 9 Write the running configuration to the startup configuration file:

Switch# copy running-config startup-config
 
   

The new password is now in the startup configuration.


Note This procedure is likely to leave your switch virtual interface in a shutdown state. You can identify this interface by entering the show running-config privileged EXEC command. To re-enable the interface, enter the interface vlan vlan-id global configuration command, and specify the VLAN ID of the shutdown interface. With the switch in interface configuration mode, enter the no shutdown command.


Step 10 You must now reconfigure the switch. If the system administrator has the backup switch and VLAN configuration files available, you should use those.


Preventing Autonegotiation Mismatches

The IEEE 802.3ab autonegotiation protocol manages the switch settings for speed (10, 100, and 1000 Mbps, 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.


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. For more information about error messages, see the system message guide for this release.


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. For more information about the errdisable recovery command, see the command reference for this release.

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 re-insert 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. For more information, see the show interfaces transceiver command in the command reference for this release.

Monitoring Temperature

The Cisco ME switch monitors the temperature conditions. The switch also uses the temperature information to control the fans. The temperature value is the temperature in the switch (not the external temperature). Enter the show env temperature privileged EXEC command to see if the temperature is okay or faulty.

On the Cisco ME-3400-12CS and ME-3400-2CS switches, you can use the show env temperature status privileged EXEC command to display the temperature value, state, and thresholds. You can configure only the yellow threshold level (in Celsius) by using the system env temperature threshold yellow value global configuration command to set the difference between the yellow and red thresholds. You cannot configure the green or red thresholds.

For more information, see the command reference for this release.

Using Ping

These sections contain this information:

Understanding Ping

Using Ping

Understanding Ping

The Cisco ME 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.

The Cisco ME switch also provides the Control Plane Security feature, which by default drops ping response packets received on user network interfaces (UNIs) or enhanced network interfaces (ENIs). However, methods are available to ping successfully from the switch to a host connected to a UNI or ENI.

Control Plane Security does not drop ping response packets to or from network node interfaces (NNIs), and no special configuration is required to enable pings to or from hosts connected to NNIs.

Using Ping

Beginning in privileged EXEC mode, use the ping command to ping another device on the network from the switch:

Command
Purpose

ping [host | address]

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

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



Note Ping is not supported on a UNI or ENI configured as an IEEE 802.1Q tunnel port.

Ping is supported on NNIs on all software images.


It is important to note that the software images available for the switch provide different options for pinging a host connected to a UNI or ENI:

Metro IP access image that supports IP routing

Metro access image

Metro base image

The next sections apply to both access ports and trunk ports.

All Software Versions

For all software images for the Cisco ME switch, you can use a Layer 3 service policy to enable pings from the switch to a host connected to a UNI or ENI.


Note For a switch running the metro IP access image, IP routing is not enabled by default and does not have to be enabled to use a Layer 3 service policy.


This example is one possible configuration:

switch# configure terminal
switch(config)# access list 101 permit ip any any
switch(config)# class-map match-any ping-class
switch(config-cmap)# match access-group 101
switch(config-cmap)# exit
switch(config)# policy-map ping-policy
switch(config-pmap)# class ping-class
switch(config-pmap-c)# police 1000000
switch(config-pmap-c)# exit
switch(config-pmap)# exit
switch(config)# int fa0/1
switch(config-if)# service-policy input ping-policy
switch(config-if)# switchport access vlan 2
switch(config-if)# no shut
switch(config-if)# exit
switch(config)# int vlan 2
switch(config-if)# ip address 192.168.1.1 255.255.255.0
switch(config-if)# end
switch# ping 192.168.1.2

Metro IP Access Image

When your switch is running the metro IP access image, you can use any of these methods:

Apply a Layer 3 service policy to a UNI or ENI.

Enable IP routing globally and ping from a switch virtual interface (SVI).

Enable IP routing and ping from a routed port.

For a sample configuration of how to add a Layer 3 service policy to a UNI or ENI, see the "All Software Versions" section.

For examples using IP routing and pinging from an SVI or a routed port, see the next sections.

IP Routing and SVI

IP routing is only supported when the switch is running the metro IP access image.

You can use this configuration to enable IP routing and enable pings from an SVI to a host connected to a UNI or ENI.

Switch# configure terminal
Switch(config)# ip routing
Switch(config)# int fa0/1
Switch(config-if)# switchport access vlan 2
Switch(config-if)# no shutdown
Switch(config-if)# int vlan 2
Switch(config-if)# ip address 192.168.1.1 255.255.255.0
Switch(config-if)# end
Switch# ping 192.168.1.2
 
   

With this configuration, a host with an IP address of 192.168.1.2 can be pinged from the switch.

IP Routing and Routed Port

You can use this configuration to enable IP routing, change a switchport to a routed port, and permit pings from the switch to a connected host:

switch# configure terminal
switch(config)# int fa0/1
switch(config-if)# no switchport
switch(config-if)# ip address 192.168.1.1 255.255.255.0
switch(config-if)# no shutdown
switch(config-if)# exit
switch(config)# ip routing
switch(config)# end 
switch# ping 192.168.1.2
 
   

Ping Responses

This response is typical of a successful ping to a host:

Switch# ping 72.20.52.3
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#
 
   

An unsuccessful ping results in this message:

Switch# ping 72.20.52.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to 172.20.52.3, timeout is 2 seconds:
. . . . .
 
   
Success rate is 0 percent (0/5)

Summary

Keep these guidelines in mind while pinging:

IP routing is available only with the metro IP access image and is disabled by default.

To ping a host in a different IP subnetwork from the switch, you must have IP routing configured to route between the subnets, and a static route to the destination might also be appropriate. If you need to enable or configure IP routing, see Chapter 36 "Configuring IP Unicast Routing."

All software versions can use a Layer 3 service policy to permit pings to and from a host connected to a UNI or ENI. For more information about policy maps, see the "Input and Output Policies" section.

If your switch is running the metro IP access image, use one of these methods to ping a host connected to a UNI or ENI:

Use a Layer 3 service policy to permit pings to and from a host connected to a UNI or ENI.

Enable global IP routing and configure a port as a routed port by using the no switchport interface configuration command.

Enable global IP routing, create an SVI, and assign an IP address to it. For more information about SVIs, see the "Switch Virtual Interfaces" section.

To end a ping session, simultaneously press and release the Ctrl, Shift, and 6 keys, and then press the X key.

Using Layer 2 Traceroute

Understanding Layer 2 Traceroute

Layer 2 Traceroute Usage Guidelines

Displaying the Physical Path

Understanding 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. It 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.


Note Layer 2 traceroute is available only on NNIs.


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 Usage 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.


Note CDP is enabled by default on NNIs. You can enable CDP on ENIs, but UNIs do not support CDP.


For a list of switches that support Layer 2 traceroute, see the "Layer 2 Traceroute Usage Guidelines" section. If any devices in the physical path are transparent to CDP, the switch cannot identify the path through these devices. For more information about enabling CDP, see Chapter 24 "Configuring CDP."

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.

Displaying the Physical Path

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

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

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


Note Layer 2 traceroute is available only on NNIs.


For more information, see the command reference for this release.

Using IP Traceroute

Understanding IP Traceroute

Executing IP Traceroute

Understanding 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 output. Intermediate switches do not show up in the 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 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 this 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.

Executing IP Traceroute

Beginning in privileged EXEC mode, follow this step to trace that the path packets take through the network:

Command
Purpose

traceroute ip host

Trace the path that packets take through the network.



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


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

Switch# traceroute ip 171.9.15.10
 
   
Type escape sequence to abort.
Tracing the route to 171.69.115.10
 
   
  1 172.2.52.1 0 msec 0 msec 4 msec
  2 172.2.1.203 12 msec 8 msec 0 msec
  3 171.9.16.6 4 msec 0 msec 0 msec
  4 171.9.4.5 0 msec 4 msec 0 msec
  5 171.9.121.34 0 msec 4 msec 4 msec
  6 171.9.15.9 120 msec 132 msec 128 msec
  7 171.9.15.10 132 msec 128 msec 128 msec
Switch#
 
   

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

Table 48-1 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.

Using TDR

Understanding TDR

Running TDR and Displaying the Results

Understanding TDR

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.

On the Cisco ME switch, TDR is supported only on the copper Ethernet 10/100 ports or on dual-purpose ports configured as 10/100/100 ports by using the RJ-45 connector.


Note Only the Cisco ME 3400-12CS and ME 3400-2CS switches have dual-purpose 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

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. For a description of the fields in the display, see the command reference for this release.


Note TDR is supported only on the copper Ethernet 10/100 ports or on dual-purpose ports configured as 10/100/100 ports by using the RJ-45 connector.


Using Debug Commands

Enabling Debugging on a Specific Feature

Enabling All-System Diagnostics

Redirecting Debug and Error Message Output


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.


Note For complete syntax and usage information for specific debug commands, see the command reference for this release.


Enabling Debugging on a Specific Feature

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 that 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 that 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

Enabling All-System Diagnostics

Beginning in privileged EXEC mode, enter this command to enable all-system diagnostics:

Switch# debug all
 
   

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.

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.

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.

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. Logging messages to the console produces very high overhead, whereas logging messages to a virtual terminal produces less overhead. Logging messages to a syslog server produces even less, and logging to an internal buffer produces the least overhead of any method.


For more information about system message logging, see Chapter 29 "Configuring System Message Logging."

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 ASICs. However, packet forwarding information can also be helpful in troubleshooting.

This is an example of the output from the show platform forward command on Gigabit Ethernet port 1 in VLAN 5 when the packet entering that port is addressed to unknown MAC addresses. The packet should be flooded to all other ports in VLAN 5.

Switch# show platform forward gigabitethernet0/1 vlan 5 1.1.1 2.2.2 ip 13.1.1.1 13.2.2.2 
udp 10 20     
Global Port Number:24, Asic Number:5
Src Real Vlan Id:5, Mapped Vlan Id:5
 
   
Ingress:
 Lookup                   Key-Used                    Index-Hit  A-Data
InptACL  40_0D020202_0D010101-00_40000014_000A0000     01FFA   03000000
L2Local  80_00050002_00020002-00_00000000_00000000     00C71   0000002B
Station Descriptor:02340000, DestIndex:0239, RewriteIndex:F005
 
   
==========================================
Egress:Asic 2, switch 1
Output Packets:
 
   
------------------------------------------
Packet 1
 Lookup                   Key-Used                    Index-Hit  A-Data
OutptACL 50_0D020202_0D010101-00_40000014_000A0000     01FFE   03000000
 
   
Port       Vlan      SrcMac          DstMac    Cos  Dscpv
Gi0/1    0005 0001.0001.0001  0002.0002.0002  
 
   
------------------------------------------
Packet 2
 Lookup                   Key-Used                    Index-Hit  A-Data
OutptACL 50_0D020202_0D010101-00_40000014_000A0000     01FFE   03000000
 
   
Port       Vlan      SrcMac          DstMac    Cos  Dscpv
Gi0/2    0005 0001.0001.0001  0002.0002.0002  
 
   
------------------------------------------
<output truncated>
------------------------------------------
Packet 10
 Lookup                   Key-Used                    Index-Hit  A-Data
OutptACL 50_0D020202_0D010101-00_40000014_000A0000     01FFE   03000000
Packet dropped due to failed DEJA_VU Check on Gi0/2
 
   

This is an example of the output when the packet coming in on Gigabit Ethernet port 1 in VLAN 5 is sent to an address already learned on the VLAN on another port. It should be forwarded from the port on which the address was learned.

Switch# show platform forward gigabitethernet0/1 vlan 5 1.1.1 0009.43a8.0145 ip 13.1.1.1 
13.2.2.2 udp 10 20
Global Port Number:24, Asic Number:5
Src Real Vlan Id:5, Mapped Vlan Id:5
 
   
Ingress:
 Lookup                   Key-Used                    Index-Hit  A-Data
InptACL  40_0D020202_0D010101-00_40000014_000A0000     01FFA   03000000
L2Local  80_00050009_43A80145-00_00000000_00000000     00086   02010197
Station Descriptor:F0050003, DestIndex:F005, RewriteIndex:0003
 
   
==========================================
Egress:Asic 3, switch 1
Output Packets:
 
   
 
   
------------------------------------------
Packet 1
 Lookup                   Key-Used                    Index-Hit  A-Data
OutptACL 50_0D020202_0D010101-00_40000014_000A0000     01FFE   03000000
 
   
Port       Vlan      SrcMac          DstMac    Cos  Dscpv
Gi0/2    0005 0001.0001.0001  0009.43A8.0145 
 
   

This is an example of the output when the packet coming in on Gigabit Ethernet port 1 in VLAN 5 has a destination MAC address set to the router MAC address in VLAN 5 and the destination IP address unknown. Because there is no default route set, the packet should be dropped.

Switch# show platform forward gigabitethernet0/1 vlan 5 1.1.1 03.e319.ee44 ip 13.1.1.1 
13.2.2.2 udp 10 20
Global Port Number:24, Asic Number:5
Src Real Vlan Id:5, Mapped Vlan Id:5
 
   
Ingress:
 Lookup                   Key-Used                    Index-Hit  A-Data
InptACL  40_0D020202_0D010101-00_41000014_000A0000     01FFA   03000000
L3Local  00_00000000_00000000-90_00001400_0D020202     010F0   01880290
L3Scndr  12_0D020202_0D010101-00_40000014_000A0000     034E0   000C001D_00000000
Lookup Used:Secondary
Station Descriptor:02260000, DestIndex:0226, RewriteIndex:0000
 
   

This is an example of the output when the packet coming in on Gigabit Ethernet port 1 in VLAN 5 has a destination MAC address set to the router MAC address in VLAN 5 and the destination IP address set to an IP address that is in the IP routing table. It should be forwarded as specified in the routing table.

Switch# show platform forward gigabitethernet0/1 vlan 5 1.1.1 03.e319.ee44 ip 110.1.5.5 
16.1.10.5
Global Port Number:24, Asic Number:5
Src Real Vlan Id:5, Mapped Vlan Id:5
 
   
Ingress:
 Lookup                   Key-Used                    Index-Hit  A-Data
InptACL  40_10010A05_0A010505-00_41000014_000A0000     01FFA   03000000
L3Local  00_00000000_00000000-90_00001400_10010A05     010F0   01880290
L3Scndr  12_10010A05_0A010505-00_40000014_000A0000     01D28   30090001_00000000
Lookup Used:Secondary
Station Descriptor:F0070007, DestIndex:F007, RewriteIndex:0007
 
   
==========================================
Egress:Asic 3, switch 1
Output Packets:
 
   
------------------------------------------
Packet 1
 Lookup                   Key-Used                    Index-Hit  A-Data
OutptACL 50_10010A05_0A010505-00_40000014_000A0000     01FFE   03000000
 
   
Port       Vlan      SrcMac          DstMac    Cos  Dscpv
Gi0/2    0007 XXXX.XXXX.0246  0009.43A8.0147 

Using the crashinfo File

The crashinfo file saves information that helps Cisco technical support representatives to debug problems that caused the Cisco IOS image to fail (crash). The switch writes the crash information to the console at the time of the failure, and the file is created the next time you boot the Cisco IOS image after the failure (instead of while the system is failing).

The information in the 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.

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

flash:/crashinfo/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 tech-support privileged EXEC command. You can delete crashinfo files by using the delete privileged EXEC command.

You can display the most recent crashinfo file (that is, the file with the highest sequence number at the end of its filename) by entering 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.