Output Queue Drops!

NullCodeNullCode Member Posts: 72 ■■□□□□□□□□
HI Guys,

I am not good with QoS, maybe someone can explain to me. I have alot of output drops on an interface that is facing a AP. So on switch, port fa0/7 an AP is connected. The switch has been configured with the default CNA profile. Can you help me, i need to tune up the QOS, but can someone explain a little in depth what is happening ?

Thank you.


Switch#sh platform port-asic stats drop fa0/7

Interface Fa0/7 TxQueue Drop Statistics
Queue 0
Weight 0 Frames 0
Weight 1 Frames 0
Weight 2 Frames 0
Queue 1
Weight 0 Frames 0
Weight 1 Frames 0
Weight 2 Frames 0
Queue 2
Weight 0 Frames 0
Weight 1 Frames 0
Weight 2 Frames 0
Queue 3
Weight 0 Frames 0
Weight 1 Frames 0
Weight 2 Frames 13953001


interface FastEthernet0/7
switchport mode trunk
switchport nonegotiate
srr-queue bandwidth share 10 10 60 20
priority-queue out
mls qos trust cos
macro description cisco-wireless
auto qos voip trust
spanning-tree bpduguard enable
end


I guess the problem is here srr-queue bandwidth share 10 10 60 20, that i should change from 20 to more, but can you please explain why this is happening only here ?
I have a lot of switches configured the same, and i do not see any drops.

Comments

  • NullCodeNullCode Member Posts: 72 ■■□□□□□□□□
    Any help with this ? Do you need more information ?
  • networker050184networker050184 Mod Posts: 11,962 Mod
    I'm not too hot with L2 QoS myself, but I'll try to help you out.

    What queue are you seeing drops in? Are you running the default queue maps?
    An expert is a man who has made all the mistakes which can be made.
  • NullCodeNullCode Member Posts: 72 ■■□□□□□□□□
    Output of the mls configuration(Default from CNA):
    mls qos map cos-dscp 0 8 16 24 32 46 48 56
    mls qos srr-queue input bandwidth 90 10
    mls qos srr-queue input threshold 1 8 16
    mls qos srr-queue input threshold 2 34 66
    mls qos srr-queue input buffers 67 33
    mls qos srr-queue input cos-map queue 1 threshold 2 1
    mls qos srr-queue input cos-map queue 1 threshold 3 0
    mls qos srr-queue input cos-map queue 2 threshold 1 2
    mls qos srr-queue input cos-map queue 2 threshold 2 4 6 7
    mls qos srr-queue input cos-map queue 2 threshold 3 3 5
    mls qos srr-queue input dscp-map queue 1 threshold 2 9 10 11 12 13 14 15
    mls qos srr-queue input dscp-map queue 1 threshold 3 0 1 2 3 4 5 6 7
    mls qos srr-queue input dscp-map queue 1 threshold 3 32
    mls qos srr-queue input dscp-map queue 2 threshold 1 16 17 18 19 20 21 22 23
    mls qos srr-queue input dscp-map queue 2 threshold 2 33 34 35 36 37 38 39 48
    mls qos srr-queue input dscp-map queue 2 threshold 2 49 50 51 52 53 54 55 56
    mls qos srr-queue input dscp-map queue 2 threshold 2 57 58 59 60 61 62 63
    mls qos srr-queue input dscp-map queue 2 threshold 3 24 25 26 27 28 29 30 31
    mls qos srr-queue input dscp-map queue 2 threshold 3 40 41 42 43 44 45 46 47
    mls qos srr-queue output cos-map queue 1 threshold 3 5
    mls qos srr-queue output cos-map queue 2 threshold 3 3 6 7
    mls qos srr-queue output cos-map queue 3 threshold 3 2 4
    mls qos srr-queue output cos-map queue 4 threshold 2 1
    mls qos srr-queue output cos-map queue 4 threshold 3 0

    mls qos srr-queue output dscp-map queue 1 threshold 3 40 41 42 43 44 45 46 47
    mls qos srr-queue output dscp-map queue 2 threshold 3 24 25 26 27 28 29 30 31
    mls qos srr-queue output dscp-map queue 2 threshold 3 48 49 50 51 52 53 54 55
    mls qos srr-queue output dscp-map queue 2 threshold 3 56 57 58 59 60 61 62 63
    mls qos srr-queue output dscp-map queue 3 threshold 3 16 17 18 19 20 21 22 23
    mls qos srr-queue output dscp-map queue 3 threshold 3 32 33 34 35 36 37 38 39
    mls qos srr-queue output dscp-map queue 4 threshold 1 8
    mls qos srr-queue output dscp-map queue 4 threshold 2 9 10 11 12 13 14 15
    mls qos srr-queue output dscp-map queue 4 threshold 3 0 1 2 3 4 5 6 7
    mls qos queue-set output 1 threshold 1 138 138 92 138
    mls qos queue-set output 1 threshold 2 138 138 92 400
    mls qos queue-set output 1 threshold 3 36 77 100 318
    mls qos queue-set output 1 threshold 4 20 50 67 400
    mls qos queue-set output 2 threshold 1 149 149 100 149
    mls qos queue-set output 2 threshold 2 118 118 100 235
    mls qos queue-set output 2 threshold 3 41 68 100 272
    mls qos queue-set output 2 threshold 4 42 72 100 242
    mls qos queue-set output 1 buffers 10 10 26 54
    mls qos queue-set output 2 buffers 16 6 17 61
    mls qos

    My guess is the bold lines are the problem. I have packets comming with CoS 0(data traffic) and those are attributed 20% of the bandwith. Then i have "priority-queue out" applied on the interface, that means that the priority queue(1) will get 100% of the bandwidth until it gets clear.

    @networker050184
    As you see, Queue 4 has the output drops.

    The thing is that, i do not know why this happens only on this switch. I have the same configuration on other switches, but i do not see the same results.


    Thank you.
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