Catalyst 3750 Software Configuration Guide, Release 12.2(55)SE

Procedure with Password Recovery Enabled

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

Step 1 Initialize the flash file system:

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:

Step 4 Display the contents of flash memory:

The switch file system appears:

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

This file contains the password definition.

Step 6 Boot up the system:

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

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

Step 8 Rename the configuration file to its original name:

Note Before continuing to Step 9, power on any connected stack members and wait until they have completely initialized. Failure to follow this step can result in a lost configuration depending on how your switch is set up.

Step 9 Copy the configuration file into memory:

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:

Step 11 Change the 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:

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

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 see which interface is in this state 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 stack:

Procedure with Password Recovery Disabled

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

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.

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• 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:

• 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:

Step 2 Load any helper files:

Step 3 Display the contents of flash memory:

The switch file system appears:

Step 4 Boot up the system:

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

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

Step 6 Enter global configuration mode:

Step 7 Change the 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:

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

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

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 see which interface is in this state 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.

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:

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

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

Step 3 Start 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 4 At the switch prompt, enter privileged EXEC mode:

Step 5 Enter the password of the failed command switch.

Step 6 Enter global configuration mode.

Step 7 Remove the member switch from the cluster.

Step 8 Return to privileged EXEC mode.

Step 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.

Step 10 Enter 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:

or

If this prompt does not appear, enter enable, and press Return. Enter setup, and press Return to start the setup program.

Step 11 Respond 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 12 When prompted for the enable secret and enable passwords, enter the passwords of the failed command switch again.

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

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

The cluster name can be 1 to 31 alphanumeric characters, dashes, or underscores.

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

Step 16 If 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 17 Start your browser, and enter the IP address of the new command switch.

Step 18 From 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:

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

Step 2 Start 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 3 At the switch prompt, enter privileged EXEC mode:

Step 4 Enter the password of the failed command switch.

Step 5 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.

Step 6 Enter Y at the first prompt.

The prompts in the setup program vary depending on the switch you selected to be the command switch:

or

If this prompt does not appear, enter enable, and press Return. Enter setup, and press Return to start the setup program.

Step 7 Respond 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 8 When prompted for the enable secret and enable passwords, enter the passwords of the failed command switch again.

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

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

The cluster name can be 1 to 31 alphanumeric characters, dashes, or underscores.

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

Step 12 If 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 13 Start your browser, and enter the IP address of the new command switch.

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

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 is 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. 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.

Use these commands, described in the command reference for this release, to monitor the PoE port status:

• show controllers power inline privileged EXEC command
• show power inline privileged EXEC command
• debug ilpower privileged EXEC command

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 t ake the port out of the error-disabled state, enter the shutdown and the no shutdown i nterface configuration commands.

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

Understanding 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.

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. For more information, see Chapter38, “Configuring IP Unicast Routing”

IP routing is disabled by default on all switches. If you need to enable or configure IP routing, see Chapter38, “Configuring IP Unicast Routing”

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

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

This example shows how to ping an IP host:

Table 49-1 describes the possible ping character output.

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.

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.

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.

Usage Guidelines

These are the 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.

For a list of switches that support Layer 2 traceroute, see the “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 Chapter26, “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 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 ]

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

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 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.

Executing IP Traceroute

Beginning in privileged EXEC mode, follow this step to trace that the path 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:

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.

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.

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.

TDR is supported only on 10/100/100 copper Ethernet ports. It is not supported on 10/100 ports, 10-Gigabit module ports, or 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

Running TDR and Displaying the Results

When you run TDR on an interface, you can run it on the stack master or a stack member.

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.

Enabling Debugging on a Specific Feature

When you enable debugging, it is enabled only on the stack master. To enable debugging on a stack member, you must start a session from the stack master by using the session switch-number privileged EXEC command. Then, enter the debug command at the command-line prompt of the stack member.

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):

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:

Alternately, in privileged EXEC mode, you can enter the undebug form of the command:

To display the state of each debugging option, enter this command in privileged EXEC mode:

Enabling All-System Diagnostics

Beginning in privileged EXEC mode, enter this command to enable 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.

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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.

When stack members generate a system error message, the stack master displays the error message to all stack members. The syslog resides on the stack master.

Note Make sure to save the syslog to flash memory so that the syslog is not lost if the stack master fails.

For more information about system message logging, see Chapter31, “Configuring System Message Logging”

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 other switch-specific information. 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.

Displaying TCAM Memory Consistency Check Errors

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

This example shows information about the TCAM memory consistency integrity on the switch:

The display provides information about TCAM portions that were checked for integrity.

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

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. Table 49-4 lists the primary types of CPU utilization problems that you can identify. It gives possible causes and corrective action with links to the Troubleshooting High CPU Utilization document on Cisco.com.

Possible Symptoms of High CPU Utilization

Note that excessive CPU utilization might result in these symptoms, but the symptoms could 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

Layer 3 switches:

• Dropped packets or increased latency for packets routed in software
• BGP or OSPF routing topology changes
• HSRP flapping

Verifying the Problem and Cause

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.

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.

For complete information about CPU utilization and how to troubleshoot utilization problems, see the Troubleshooting High CPU Utilization document on Cisco.com.

Troubleshooting Power over Ethernet (PoE)

Troubleshooting Stackwise