Cisco Catalyst 4000 Series Switches

Field Notice: Catalyst 4000 Ports Lose Active VLAN State Resulting in Packet Loss

Updated September 19, 2001

July 16, 2001

Products Affected









Problem Description

A Catalyst 4000 Series Switch (including the Catalyst 2948, 2980G, 4003, 4006, 4912G, and WS-X5410 Line Card for the Catalyt 5500) lose active VLAN state on one or more ports.


The switch software updates the active VLAN state of the switch in response to local and remote VLAN configuration changes. Under certain conditions, an update to the VLAN state of a port fails and the affected port will lose its active VLAN state.

Spanning-Tree Protocol (STP), Cisco Discovery Protocol (CDP), and other control traffic will continue to operate normally.

Problem Symptoms

When an affected port loses its active VLAN state, it exhibits the following symptoms:

  1. All traffic forwarded on an affected port is transmitted untagged in the native VLAN.

  2. All untagged traffic received on an affected port is dropped.

  3. All tagged traffic received on an affected port is received and forwarded correctly.

An affected port typically loses VLAN configuration on one of the four supported protocol buckets. The protocol buckets are partitioned as follows:

  • First Protocol Bucket - IP

  • Second Protocol Bucket - IPX

  • Third Protocol Bucket - All Other protocols (Appletalk, Vines, DECNET, and so on)

  • Fourth Protocol Bucket - Management Traffic (STP, VLAN Trunking Protocol (VTP), CDP, and so on)

Only traffic in the affected protocol bucket will exhibit the symptoms described above. In certain circumstances, the fourth protocol bucket is affected and will create a loop due to asymmetric connectivity.

Symptoms of the issue on the WS-X5410 (Nine-port Gigabit Blade) are as follows:

  • One of the nine external ports will lose active VLAN state for one of the four protocol buckets and exhibits the transmit/receive characteristics described above.

  • An internal connection to the backplane will lose active VLAN state.

  • A WS-X5410 in a single-bus slot (slots 6-12 of a WS-C5500 chassis) will experience a total loss of connectivity. A WS-X5410 in a multiple-bus slot will experience a partial loss of connectivity depending upon the distribution of traffic across the three internal backplane connections.

  • The MAC addresses of impacted traffic appears in VLAN0 in the output of the show cam dynamic command.

Symptoms of the issue on a Catalyst 4000 Series Switch (2948G, 2980G, 4912G, WS-X4012 Supervisor and WS-X4013 Supervisor) are as follows:

  • An external port loses active VLAN state on one of the four protocol buckets and exhibits the transmit/receive characteristics described above.

  • An internal port on the WS-X4013 Supervisor loses active VLAN state and impacts connectivity to a group of ports across all modules. See DDTS CSCdt80707 below.


This problem has been fixed in Catalyst 4000 software releases 5.5(10), 6.3(1), and 6.2(3).

Cisco recommends customers upgrade to a minimum of release 5.5(10). In addition to fixing caveat CSCdt80707, release 5.5(10) and above have enhanced diagnostics capabilities that allow the switch to identify latent hardware component failures. Thus preventing unnecessary hardware replacements. Example below:

  1. Download the 5.5(10) image and change the configuration to boot 5.5(10).

  2. Reset the box from the switch CLI.

  3. The box will reset, boot 5.5(10), and run Power On Self Test (POST).

  4. If POST detects any failures, the supervisor will indicate the faulty module number and an error.

  5. Replace the indicated faulty module, and schedule it for Engineering Failure Analysis (EFA).

  6. EFA will provide root cause analysis that identifies the faulty component on the suspect module.

To download Catalyst releases, please go to the Software Download pages located on CCO.


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




Cat4k or WS-X5410 blade may stop forwarding user traffic.


Partial loss of connectivity on a 4006 switch.

How To Upgrade Software

For instructions on upgrading Catalyst OS on 4000 and 5000 switches, please see the Working with Software Images section of the Catalyst users guide.

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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