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The useful sources of information about switch operation are the LEDs on the front panel and the statistics available from the web interface, command-line interface (CLI), or SNMP workstation. The LEDs indicate failures in the power-on self-test (POST), port-connectivity problems, and overall performance of the switch. The statistics identify errors per port that can be used to troubleshoot typical switch problems. See the "LEDs" section in the "Introduction" chapter for a full description of the switch LEDs.
This chapter discusses troubleshooting problems with the following topics:
The POST is composed of eight tests that run each time the switch is powered up. These tests check the most important system components before the switch begins forwarding packets. The "Reading POST Results" section in the "Installation" chapter describes how to read a POST failure.
Table 8-1 lists the eight POST tests and their associated LEDs.
| Switch LED | Component Tested |
LED 1x | DRAM |
LED 2x | Flash memory |
LED 3x | Switch CPU |
LED 4x | System board |
LED 5x | CPU interface ASIC |
LED 6x | Switch core ASIC |
LED 7x | Ethernet controller ASIC |
LED 8x | Ethernet interfaces |
Common switch problems fall into the following categories:
Table 8-2 describes how to detect and resolve these problems.
| Symptom | Possible Cause | Resolution |
|---|---|---|
Poor Performance or Excessive Errors | Autonegotiation Mismatch | See the "Identifying an Autonegotiation Mismatch" section in this chapter. |
| Cabling Distance Exceeded Port statistics show excessive frame check sequence (FCS), late-collision, or alignment errors. For 100BaseTX connections: |
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| Reduce the cable length to within the recommended distances. |
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| See your 100BaseT repeater documentation for cabling guidelines. |
| For 10BaseT connections: The distance between the port and the attached device exceeds 100 meters. | Reduce the cable length to within the recommended distances. |
| Bad Adapter in Attached Device Excessive errors found in port statistics. |
Run adapter card diagnostic utility. |
No Connectivity | Incorrect or Bad Cable The following are indicated by no link at both ends:
|
See the "Crossover and Straight-Through Cable Pinouts" section in the "Technical Specifications" appendix for the correct pinouts and the proper application of cross-over vs. straight-through cables. |
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| Replace with a tested good cable. |
| STP checking for possible loops. | Wait 30 seconds for LED to turn green. |
System LED is Amber, and All Port LEDs Are Off. | Switch Not Responding Due to Corrupted Firmware | Attach a monitor to the serial port to display the switch boot loader. See the "Recovering from Corrupted Software" section of this chapter for software upgrade instructions. |
Amber Expansion Slot LED | Module not seated in expansion slot. | Tighten the thumb screws on the module front panel. |
Unreadable Characters on the Management Console | Incorrect Baud Rate | Reset the emulation software to |
The IEEE 802.3u autonegotiation protocol manages the switch settings for speed (10 Mbps or 100 Mbps) and duplex (half or full). There are situations when this protocol can incorrectly align these settings, reducing performance. A mismatch occurs when:
To maximize switch performance and ensure a link, follow one of these guidelines when changing the settings for duplex and speed:
An autonegotiation mismatch of the duplex setting can reduce performance or cause no link. You can identify a duplex mismatch by checking the port statistics for the following errors:
Follow these steps to determine if slow performance is caused by autonegotiation:
Step 1 Connect a PC with emulation software to the switch console port or display the command-line interface by using Telnet.
Step 2 Display the CLI.
Step 3 Enter the enable command to enter the privileged EXEC command mode:
switch> enable
switch#
Step 4 Enter the show controllers ethernet-controller command, identifying one of the connected ports:
switch# show controllers ethernet-controller fa0/4
Transmit Receive
26869777 Bytes 402753236 Bytes
460 Unicast frames 1 Unicast frames
45408 Multicast frames 198165 Multicast frames
12207 Broadcast frames 0 Broadcast frames
Discarded frames 0 No bandwidth frames
Too old frames 0 No buffers frames
Deferred frames 0 No dest, unicast
0 1 collision frames 0 No dest, multicast
0 2 collision frames 0 No dest, broadcast
0 3 collision frames 1 Alignment errors
0 4 collision frames 0 FCS errors
0 5 collision frames 0 Collision fragments
0 6 collision frames
0 7 collision frames 0 Undersize frames
0 8 collision frames 198166 Minimum size frames
0 14 collision frames 0 Oversize frames
0 15 collision frames
0 16 Excessive collisions
1102 Late collisions
Note the high number of late collisions. According to the guidelines, late collisions could be a half-duplex port trying to communicate with a full-duplex port.
Step 5 Enter the show interface command to check the duplex setting of the port:
switch# show interface fa0/4
FastEthernet0/4 is up, line protocol is up Hardware is Fast Ethernet, address is 0eef.4e19.31ea
(bia e002.320a.1102) MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive not set Half-duplex, 100Mb/s, 100BaseTX/FX ARP type: ARPA, ARP Timeout 04:00:00 Last input 4d16h, output 00:00:00, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 ...
The port is transmitting and receiving in half duplex.
Step 6 Use Telnet to log into the switch with the port that this port is connected to.
Step 7 If the other switch is a Catalyst 2900 series switch, you can enter the show interface command for the connected port:
Switch# show interface fa0/8
FastEthernet0/8 is up, line protocol is up Hardware is Fast Ethernet, address is 00e0.1e69.22c8
(bia 00e0.1e69.22c8) MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive not set Full-duplex, 100Mb/s, 100BaseTX/FX ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:00, output 00:00:18, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 1237000 bits/sec, 34 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec ...
Step 8 The connected port is operating in full duplex, and the device at the other end of the connection is operating in half duplex. Confirm the mismatch by checking this port for FCS errors. Enter the show controllers ethernet-controller command for the port:
Switch# show controllers ethernet-controller fa0/8
Transmit Receive
2698618 Bytes 46540972 Bytes
2065 Unicast frames 15305 Unicast frames
7497 Multicast frames 2116545 Multicast frames
23 Broadcast frames 1722720 Broadcast frames
0 Discarded frames 0 No bandwidth frames
0 Too old frames 0 No buffers frames
0 Deferred frames 12826 No dest, unicast
0 1 collision frames 225729 No dest, multicast
0 2 collision frames 17 No dest, broadcast
0 3 collision frames 0 Alignment errors
0 4 collision frames 2245 FCS errors
0 5 collision frames 0 Collision fragments
0 6 collision frames
0 7 collision frames 0 Undersize frames
0 8 collision frames 1800540 Minimum size frames
0 9 collision frames 263844 65 to 127 byte frames ...
Step 9 The duplex settings for these ports do not match. Use the CLI or the web-based manager software to match the settings for the duplex and speed parameters. The "Port Configuration" section in the "Web-Based Management" chapter describes how to use manager software to change these parameters.
The recovery procedures in this section require that you have physical access to the switch.
Switch software can be corrupted during an upgrade, and it is possible to download the wrong file. In both cases, the switch does not pass POST, and there is no connectivity.
The following procedure uses XMODEM to recover from a corrupt or mistaken image file. This procedure is largely dependent on the emulation software you are using.
Step 1 Connect a PC with terminal emulation software supporting the XMODEM Protocol to the console port.
Step 2 Set the line speed on the emulation software to 9600 baud.
Step 3 Unplug the power cord from the back of the switch.
Step 4 Press and hold in the Mode button, and at the same time, reconnect the power cord to the switch. You can release the Mode button a second or two after the LED above port 1x goes off. The following message appears:
Image not found
Step 5 Although the switch did not boot, you can still use the boot loader to enter commands. Enter the copy xmodem command to copy the software image into Flash memory.
switch: copy xmodem: flash:image_filename
Step 6 When the XMODEM request appears, use the appropriate command on the terminal-emulation software to start the transfer.
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 console port on the back of the switch. See the "Connecting to the 100BaseFX Ports" section in the "Installation" chapter for more information.
Step 2 Set the line speed on the emulation software to 9600 baud.
Step 3 Unplug the power cord from the back of the switch.
Step 4 Hold down the Mode button, and at the same time reconnect the power cord to the switch. You can release the Mode button a second or two after the LED above port 1x goes off. Several lines of information about the software appear, as do instructions:
The system has been interrupted prior to initializing the flash file system. The following commands will initialize the flash file system, and finish loading the operating system software: flash_init load_helper boot
Step 5 Enter the flash_init command to initialize the Flash file system:
switch: flash_init
Step 6 If you had set the line speed for the console port to anything other than 9600, it has been reset to that speed. Change the line speed on your emulation software to match that of the switch.
Step 7 Enter the load_helper command to load any helper files:
switch: load_helper
Step 8 Display the contents of Flash by entering the dir command:
switch: dir flash:
The switch file system is displayed:
Directory of flash: 2 -rwx 843947 Mar 01 1993 00:02:18 C2900XL-h-mz-112.8-SA 4 drwx 3776 Mar 01 1993 01:23:24 html 66 -rwx 130 Jan 01 1970 00:01:19 env_vars 68 -rwx 1296 Mar 01 1993 06:55:51 config.text 1728000 bytes total (456704 bytes free)
Step 9 Rename the configuration file to config.text.old. This file contains the password definition.
switch: flash:config.text flash:config.text.old
Step 10 Boot the system with the boot command:
switch: boot
You are prompted to start the setup program. Enter N at the prompt:
Continue with the configuration dialog? [yes/no]: N
Step 11 At the switch prompt, change to privileged EXEC mode by entering the enable command:
switch> enable
Step 12 Rename the configuration file to its original name with the rename command:
switch# rename flash:config.old flash:config.text
Step 13 Copy the configuration file into memory with the copy command:
switch# copy flash:config.text system:running-config
Source filename [config.text]?
Destination filename [running-config]?
Press Return in response to the confirmation prompts.
Step 14 The configuration file is now reloaded, and you can use the normal commands to change the password. Enter the configuration terminal command to change to configuration mode:
switch# configuration terminal
Step 15 Enter the enable password command to change the password:
switch(config)# enable password string
where string is the password.
Step 16 Write the running configuration to the startup configuration file by using the copy command:
switch(config)# copy running-config startup-config
The new password is now included in the startup configuration.
New Catalyst 2900 series XL software releases can be downloaded from Cisco Connection Online, the Cisco Systems customer web site available at the following URLs:
From the CCO home page, select Service and Support. On the next page, select
Software Center, and then select Switching Products. Find the Catalyst 2900 series XL heading, and select it to display the available software images.
Posted: Tue May 11 12:08:09 PDT 1999
Copyright 1989-1999©Cisco Systems Inc.