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Noticing Input Queue Drops and Flushes on Interface VLAN...

I have recently enabled QOS on my 6509 (running Hybrid mode).I have noticed that on some of my layer 3 Interface VLANs I am seeing some Input Queue drops and Flushes. Sometimes only Flushes and no drops or Drops and no Flushes and sometimes both. I checked out the Show Process Cpu and the only thing I can see that might be an issue is the IP Input Process (Checks process switching), it is rather large. I also noticed that on some Interface VLANs that do not have QOS enabled on them I see drops and flushes. I do not have any modification on the Input Queue (Queue is set for default of 75). Do I need to increment the Input Hold Queue? If so is their a formula that should guide me as to what value to make the Input Hold Queue? Is this the right area I should be looking at to resolve this ? Has anyone come across this issue of Input Queue Drops and Flushes?? Also, I cannot find anything on the Cisco website on what a "Flush" is. Can anyone elaborate on what a flush is and what might initiate it? Thanks...


Re: Noticing Input Queue Drops and Flushes on Interface VLAN...

If this happened right after enabling QoS, you probably enabled a QoS feature that cant be processed in hardware. All of these packets then are being sent to the CPU in the 'ip input' process. If the CPU is busy, the input queue for the VLAN will climb up and you'll get drops.

What kind of SUP/MSFC are you using? What did you configure for QoS?


Re: Noticing Input Queue Drops and Flushes on Interface VLAN...

I have a Sup1a (WS-X6K-SUP1A-2GE) and MSFC running c6msfc-jk2sv-mz.121-23.E4.bin code. I enabled AuotQOS on the 6509 and setup class-maps and policy maps on only one of the interface Vlans. I am noticing on other interface Vlans that I do not have QOS on, I see drops and flushes. I an not leading to believe that this is a QOS issue. I am not sure if these errors occurred after I applied the QOS or before. Do you have further info on what flushes are? What value of Hold Queue should I increase the queue to? This problem is not consistant throughout the day. It occurs maybe once or twice a day. I think that increasing the Hold queue will solve this. I just want to make sure that I am not missing anything else....

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