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New Member

Cisco 3750 Auto-QoS Egress Discards

Hello all,

I have an issue where I'm seeing output discards on pretty much all my ports configured for QoS. The switches are cisco WS-C3750V2-48PS running 12.2(50)SE1. There are four switches stacked using stack cables. The QoS implemeted was auto-qos with no modifications to the standard config. All ports are in queue-set 1. The phones connected are Cisco 7942's. Already did the standard check for speed duplex mismatch, crc's, runts, giants, etc...No discards before the QoS was applied. No bug ID's I could find regarding these switches and this IOS version. The one thing noticed is that 99% of all the drops are from queue's 2 and 4 or 1 and 3 doing the below command. Looking for any ideas.

**I've limited the cut and paste as to not clutter the discussion until someone requests something else**

Thanks,

James

show platform port-asic stats drop

Port 18 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 1852

  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 57788

interface FastEthernet1/0/18

switchport access vlan 100

switchport voice vlan 101

speed 100

duplex full

srr-queue bandwidth share 10 10 60 20

priority-queue out

mls qos trust device cisco-phone

mls qos trust dscp

auto qos voip cisco-phone

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Cisco 3750 Auto-QoS Egress Discards

Please post the output from typing:

show mls qos interface fa1/0/18 statistics

and

show mls qos maps

Super Bronze

Cisco 3750 Auto-QoS Egress Discards

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Posting

Enabling QoS on a 3750 splits buffer resources across 4 queues instead of just 1 queue.  Likely the default buffer re-allocations doesn't well support your traffic in the 4 queues.  You may be able to mitigate the problem by re-assigning buffer resources, but that's not guaranteed.

Cisco 3750 Auto-QoS Egress Discards

James,

I am also running 122(50) SE1 on some of my switches, I notice in your interface configuration there is not

"service-policy input AutoQoS-Police-CiscoPhone" which is one of the things generated by the Auto Qos command.

with the  sh platform port-asic stats drop

I get the following; BTW the switch has been up 33 weeks, so really not that many drops, most of the Ip phones are 7962s

I am just wondering if it is working as it should, what sort of PC traffic do you have on your interfaces, does anybody complain about slowness etc?

Port-asic Port Drop Statistics - Summary
========================================
  RxQueue 0 Drop Stats: 0
  RxQueue 1 Drop Stats: 0
  RxQueue 2 Drop Stats: 0
  RxQueue 3 Drop Stats: 0

  Port  0 TxQueue Drop Stats: 0
  Port  1 TxQueue Drop Stats: 0
  Port  2 TxQueue Drop Stats: 535404
  Port  3 TxQueue Drop Stats: 7149
  Port  4 TxQueue Drop Stats: 8572
  Port  5 TxQueue Drop Stats: 3011
  Port  6 TxQueue Drop Stats: 0
  Port  7 TxQueue Drop Stats: 66760
  Port  8 TxQueue Drop Stats: 0
  Port  9 TxQueue Drop Stats: 5983
  Port 10 TxQueue Drop Stats: 5867
  Port 11 TxQueue Drop Stats: 0
  Port 12 TxQueue Drop Stats: 7102
  Port 13 TxQueue Drop Stats: 0
  Port 14 TxQueue Drop Stats: 0
  Port 15 TxQueue Drop Stats: 2083
  Port 16 TxQueue Drop Stats: 419
  Port 17 TxQueue Drop Stats: 44784
  Port 18 TxQueue Drop Stats: 2300
  Port 19 TxQueue Drop Stats: 10876
  Port 20 TxQueue Drop Stats: 2271
  Port 21 TxQueue Drop Stats: 57697
  Port 22 TxQueue Drop Stats: 52418
  Port 23 TxQueue Drop Stats: 24695
  Port 24 TxQueue Drop Stats: 1729
  Port 25 TxQueue Drop Stats: 3720

New Member

Re: Cisco 3750 Auto-QoS Egress Discards

Here are the stats after changing the SRR settings yesterday from 10.10.60.20

interface FastEthernet1/0/24

switchport access vlan 100

switchport voice vlan 101

srr-queue bandwidth share 10 20 10 60

priority-queue out

mls qos trust device cisco-phone

mls qos trust dscp

auto qos voip cisco-phone

spanning-tree portfast

YOW02-SWM-001#show platform port-asic stats drop fastEthernet 1/0/24

  Interface Fa1/0/24 TxQueue Drop Statistics
    Queue 0
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 1
      Weight 0 Frames 31512
      Weight 1 Frames 0
      Weight 2 Frames 1853
    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 66351

New Member

Re: Cisco 3750 Auto-QoS Egress Discards

Wait a minute. These may be old stats as I don't think you can clear the show platform counters like you can the show mls counters.

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