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Cisco Catalyst 3550 Series Switches

Field Notice: Spanning Tree Protocol Failures in Catalyst 3550 Models Manufactured During a Specific Time Frame


Revised April 18, 2003

August 30, 2002


Products Affected

Product

Comments

WS-C3550-12T

If the switch was manufactured within the Date Codes listed below, it may be affected. Refer to Background.

WS-C3550-12G

If the switch was manufactured within the Date Codes listed below, it may be affected. Refer to Background.

WS-C3550-24-EMI

If the switch was manufactured within the Date Codes listed below, it may be affected. Refer to Background.

WS-C3550-24-SMI

If the switch was manufactured within the Date Codes listed below, it may be affected. Refer to Background.

WS-C3550-48-SMI

If the switch was manufactured within the Date Codes listed below, it may be affected. Refer to Background.

WS-C3550-48-EMI

If the switch was manufactured within the Date Codes listed below, it may be affected. Refer to Background.

Problem Description

A known quantity of the Catalyst 3550 models listed above contain a memory management error that results in the corruption of the destination MAC address of 802.1d and 802.1w/802.1s Spanning Tree BPDUs. Consequently, Spanning Tree BPDUs are not processed by the appropriate switches and cannot be relied on to prevent network loops. The Spanning Tree Protocol must be enabled and there must be a loop in the network that passes through the affected Catalyst 3550 switch for this problem to occur.

The following two products do not have the memory management error:

  • WS-C3550-24-DC-SMI

  • WS-C3550-24-FX-SMI

Background

A manufacturing process error allowed a maximum of 6000 switches that contain this memory management error to be built and shipped to customers. Approximately 14500 switches were manufactured and shipped to customers in the specific time period correlated to this process error. As a result, it has been determined that a maximum of 6000 switches that have this problem are known to be contained within this listing of 14500 switches. The complete list of the possibly affected date codes is contained below.

Problem Symptoms

A spanning-tree loop will occur in the network, causing traffic levels to increase and users to not be able to send data. In most cases, switch management will only be possible via the console port due to looping packets.

Workaround/Solution

To follow the link below to download software, you must be a registered user and you must be logged in.

To avoid this problem, it is mandatory to upgrade possibly affected switches to Cisco IOS® Software Release 12.1(11)EA1 or later. When released, the software will be available in the Software Center.

DDTS

To follow the bug ID link below and see detailed bug information, you must be a registered user and you must be logged in.

DDTS

Description

CSCdy21905 (registered customers only)

Spanning Tree Protocol failure detected in some Cat.C3550 switches.

How To Identify Hardware Levels

All of the possibly affected units are contained within the following nine date codes. See How to Identify Date Codes below for further details.

Date Code

Date Code

Date Code

CAT0624 or CHK0624

CAT0625 or CHK0625

CAT0626 or CHK0626

CAT0627 or CHK0627

CAT0628 or CHK0628

CAT0629 or CHK0629

CAT0630 or CHK0630

CAT0631 or CHK0631

CAT0632

If the date code on a particular switch is not one that is listed in the table above, then this switch does not require the Cisco IOS software upgrade for the fix. If the date code on a particular switch is listed in date codes table, then it may or may not be affected. In this case, please refer to the affected serial numbers spreadsheet to determine if the switch requires a Cisco IOS software upgrade.

Note: This spreadsheet is in Microsoft Excel format.

Note: There are two other methods to identify if a switch requires the Cisco IOS software upgrade: a Deviation Sticker or Loopback Test diagnostic. Both options are detailed below.

Deviation D063913: The Deviation Sticker denotes switches that have successfully completed the screening and test process for the STP failure. Deviation Stickers will identify switches that are within the Date Code range, but were either not found to have the failure or were upgraded to the Cisco IOS Software release that fixes this issue. The deviation sticker will be affixed to the shipping box and directly on the switch chassis.

Loopback Test: Test for a spanning-tree BPDU error. A crossover cable should be connected between two unused access ports. In this case, FastEthernet0/1 and FastEthernet0/2 are configured as access ports and are connected by a crossover cable. See RJ-45 Cables for information on Ethernet RJ-45 crossover pinouts. The interface configuration is shown below:

Switch#show run interface FastEthernet0/1
     Building configuration...
     
     Current configuration : 72 bytes
     !
     interface FastEthernet0/1
     switchport mode access
     no ip address
     end
     
     Switch#show run interface FastEthernet0/2
     Building configuration...
     
     Current configuration : 72 bytes
     !
     interface FastEthernet0/2
     switchport mode access
     no ip address
     end

If, after 30 seconds, one of the port LEDs turns amber and the other stays green, the switch is working correctly, either because it does not have the problem or already has the Cisco IOS software upgrade that corrects the problem. If, after 30 seconds, both of the LEDs turn green and flash rapidly, the Cisco IOS software will need to be upgraded. This can also be verified by looking at the output from the following commands. If the switch is working correctly, the number of BPDUs received on the blocked port will be a non-zero number and will increase every two seconds, using the default timers

WORKING_Switch#show spanning-tree interface FastEthernet 0/1 detail
     Port 1 (FastEthernet0/1) of VLAN0001 is forwarding
     Port path cost 19, Port priority 128, Port Identifier 128.1.
     Designated root has priority 32769, address 000a.4107.7400
     Designated bridge has priority 32769, address 000a.4107.7400
     Designated port id is 128.1, designated path cost 0
     Timers: message age 0, forward delay 0, hold 0
     Number of transitions to forwarding state: 1
     BPDU: sent 237, received 1
     ^^^^^^^^^^^^^^^^^^^^^^^^^^ Port is forwarding and sending BPDUs correctly.
     
     WORKING_Switch#show spanning-tree interface FastEthernet 0/2 detail
     Port 2 (FastEthernet0/2) of VLAN0001 is blocking
     Port path cost 19, Port priority 128, Port Identifier 128.2.
     Designated root has priority 32769, address 000a.4107.7400
     Designated bridge has priority 32769, address 000a.4107.7400
     Designated port id is 128.1, designated path cost 0
     Timers: message age 1, forward delay 0, hold 0
     Number of transitions to forwarding state: 0
     BPDU: sent 1, received 242
     ^^^^^^^^^^^^^^^^^^^^^^^^^^ Port is blocking and receiving BPDUs correctly.

On a switch that is experiencing the problem, the number of BPDUs received on each port will stay at 0 (zero), and both ports will be forwarding.

PROBLEM_Switch#show spanning-tree interface FastEthernet 0/1 detail
     Port 1 (FastEthernet0/1) of VLAN0001 is forwarding
     Port path cost 19, Port priority 128, Port Identifier 128.1.
     Designated root has priority 32769, address 000a.4107.7400
     Designated bridge has priority 32769, address 000a.4107.7400
     Designated port id is 128.1, designated path cost 0
     Timers: message age 0, forward delay 0, hold 0
     Number of transitions to forwarding state: 1
     BPDU: sent 24, received 0
     ^^^^^^^^^^^^^^^^^^^^^^^^^^ No BPDUs received. Port is forwarding.
     
     PROBLEM_Switch#show spanning-tree interface FastEthernet 0/2 detail
     Port 2 (FastEthernet0/2) of VLAN0001 is forwarding
     Port path cost 19, Port priority 128, Port Identifier 128.2.
     Designated root has priority 32769, address 000a.4107.7400
     Designated bridge has priority 32769, address 000a.4107.7400
     Designated port id is 128.2, designated path cost 0
     Timers: message age 0, forward delay 0, hold 0
     Number of transitions to forwarding state: 1
     BPDU: sent 26, received 0
     ^^^^^^^^^^^^^^^^^^^^^^^^^^ No BPDUs received. Port is forwarding.

How to Identify Date Codes

Date Codes are used to identify the location and specific week in which a switch was manufactured. The Date Codes are integrated in the first 7 characters of an 11 character System Serial Number: CHK0624A275. The first three letters represent the manufacturing location (CHK). The four subsequent numbers are the year (06) and the week (24) a switch was manufactured (0624).

Where to Find Serial Number on Switch

Serial Numbers can be found in these locations.

  1. The packout box

  2. The back of the switch

  3. If switch is already installed in network, Telnet to Unit, or Connect directly to switch console, and type the following command:

    switch#show version | include serial
        Motherboard serial number: CAT0625027D
        Power supply serial number: LIT062103KJ
        System serial number: CHK0625V224
    

    Or use the following command, and the serial number is near bottom of output:

    switch#show version
        Cisco Internetwork Operating System Software 
        IOS (tm) C3550 Software (C3550-I5Q3L2-M), Version 12.1(9)EA1c, RELEASE SOFTWARE (fc1)
        Copyright (c) 1986-2002 by cisco Systems, Inc.
        Compiled Tue 28-May-02 10:31 by antonino
        Image text-base: 0x00003000, data-base: 0x00685778
    
        ROM: Bootstrap program is C3550 boot loader
    
        top_5 uptime is 1 minute
        System returned to ROM by power-on
        System image file is "flash:c3550-i5q3l2-mz.121-9.EA1c/c3550-i5q3l2-mz.121-9.EA1c.bin"
    
        cisco WS-C3550-24 (PowerPC) processor (revision D0) with 65526K/8192K bytes of memory.
        Processor board ID CHK0625V224
        Last reset from warm-reset
        Bridging software.
        Running Layer2/3 Switching Image
    
        Ethernet-controller 1 has 12 Fast Ethernet/IEEE 802.3 interfaces
    
        Ethernet-controller 2 has 12 Fast Ethernet/IEEE 802.3 interfaces
    
        Ethernet-controller 3 has 1 Gigabit Ethernet/IEEE 802.3 interface
    
        Ethernet-controller 4 has 1 Gigabit Ethernet/IEEE 802.3 interface
    
        24 FastEthernet/IEEE 802.3 interface(s)
        2 Gigabit Ethernet/IEEE 802.3 interface(s)
    
        The password-recovery mechanism is enabled.
        384K bytes of flash-simulated non-volatile configuration memory.
        Base ethernet MAC Address: 00:0A:41:07:74:00
        Motherboard assembly number: 73-5700-08
        Power supply part number: 34-0966-02
        Motherboard serial number: CAT0625027D
        Power supply serial number: LIT062103KJ
        Model revision number: D0
        Motherboard revision number: C0
        Model number: WS-C3550-24-EMI
        System serial number: CHK0625V224
        Configuration register is 0x10F
    

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

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