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The %SYS-4-P2_WARN: 1/Blocked queue (tx) on port error message is displayed on a Cisco Catalyst 4000 series switch running CatOS

Core issue

These errors indicate a hardware problem or one of these problems:

  • Duplex mismatch  
  • Faulty cable   
  • Type 1 cabling  
  • Faulty ports  
  • Hardware problem of an external connected device
  • Clock failure on the Supervisor

These errors are most commonly caused by a physical layer  problem that is responsible for the back-up of a considerable amount of traffic to the internal K1  gigaports. K1 ASICs are the main chips that control the switch. Generally, the  blockedTXQcount increments due to a configuration issue or faulty cabling.

In a normal environment, the Tx queue can only be blocked for approximately 20 seconds. A longer blockage indicates a significant problem. As a result, the blocked Tx queue count increments if the Tx queue has not drained for the gigaport in 35 seconds.

Conditions that can cause the blockedTXQcount to increment include front panel port  misconfigurations, a duplex mismatch, cabling, faulty ports, faulty cabling, a bad  line card and hardware problems related to an externally connected device.

Resolution

To resolve this error, perform any of these workarounds: 

  • Issue the show port counters command and verify whether values under the Xmit-Err column increases. If the value under this column increases then the problem is that traffic from a high bandwidth link being switched to a lower bandwidth link, or traffic from multiple inbound links being switched to a single outbound link. This error is an indication that the internal send (Tx) buffer is full. Check the Duplex and speed values configured.
  • Reseat the module and perform the diagnostic test.
  • Replace the cable on the port that generates the errors with a different, known good cable.
  • Reset the blade on the slot that generates the errors and the Supervisor Engine.

If the issue persists, contact Cisco Technical Support.


Version history
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Last update:
‎06-17-2009 10:14 PM
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