QoS query - 3560 switch

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Jun 18th, 2008
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Hi

I have a query re QoS settings on a 3560 switch. The switch has PCs and VOIP phones attached.


The 3560 is configured with what is a basically an AutoQos config. The dscp mappings, queue thresholds etc are all there in the 'sh run'. However, a 'sh mls qos queing interface f0/1' ( f0/1 is the main uplink port) returned the following:



FastEthernet0/1

Egress Priority Queue : disabled

Shaped queue weights (absolute) : 25 0 0 0

Shared queue weights : 25 25 25 25

The port bandwidth limit : 100

The port is mapped to qset : 1



This concerned me. With VOIP I would have expected the priority queue here to be enabled. It isn't. The weights are all equal too.

Can anyone tell me if this is a matter of concern - should I enable the Egress Priority Queue?


Regards

Paul

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4rmorris Wed, 06/18/2008 - 05:06
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I would turn on the priority queue on the interface:

int fa0/1

priority-queue out


The auto-qos config should adjust the weights. This is the queuing config on my 3560 fastE interface after applying auto qos voip trust to the interface:


srr-queue bandwidth share 10 10 60 20

srr-queue bandwidth shape 10 0 0 0

priority-queue out

auto qos voip trust


So without seeing your actual configuration, it doesn't sound like the auto qos config is applied.


You could also try the smartports macros to get recommended configurations for switch ports for different situations:


http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_see/configuration/guide/swmacro.html


Regards,


Ryan Morris

PDEdwards Wed, 06/18/2008 - 06:22
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Thanks - if you have the patience here's the QoS config:


mls qos map cos-dscp 0 8 16 26 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


interface FastEthernet0/1

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,171,301,304,512,1001-1005

switchport mode trunk

duplex full

speed 10

mls qos trust dscp


It's not really auto-qos, it's ripped off an auto qos config on another switch. I don't think the auto qos voip trust command is applicable here as it's an uplink port.


My question now is - if I setup a priority queue on f0/1 how will this affect the values set in the 4 output queues defined in the global qos config? (There is no reference to a priority queue in this global QoS config)


Thanks and Regards,

Paul



4rmorris Wed, 06/18/2008 - 09:24
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So this config does a lot of mapping of cos values to queues and thresholds, but it doesn't actually configure the bandwidth queuing ratios on the interfaces. To do that, you need the interface commands I provided above.


The "auto qos voip trust" interface command is actually designed for an interface to another trusted device, i.e. a switch uplink or a router. So it would make sense to use it on this link.


As I mentioned, another easy way to apply best practice configuration to the uplink interface would be the cisco-switch smartports macro:


int fa0/1

macro apply cisco-switch $native_vlan


That command macro actually includes auto qos voip trust as a subcommand.


Regards,


Ryan

Collin Clark Wed, 06/18/2008 - 09:45
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One thing to add to Ryan's post is you might also need to add mls qos trust dscp (defaults to trusting cos). Like Ryan stated it depends on your interface config (and in this case the phone/trust point).

PDEdwards Thu, 06/19/2008 - 02:25
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Thanks - I had assumed the threshold part of the queue mapping was actually applied globally and referred to queing priorities.


This has got me thinking!

if you don't mind can I refer you to the QoS config on one of our 2950 switches:


wrr-queue bandwidth 20 1 80 0

wrr-queue cos-map 1 0 1 2 4

wrr-queue cos-map 3 3 6 7

wrr-queue cos-map 4 5

mls qos map cos-dscp 0 8 16 26 32 46 48 56

ip subnet-zero


interface GigabitEthernet0/1

switchport trunk allowed vlan 1,100,138,287,1001-1005

switchport mode trunk

mls qos trust dscp



I had assumed that the 'wrr-queue bandwidth 20 1 80 0' part of the config would be applied

globally to each interface on the switch. On a 2950 there is no interface level command to set queuing, so how does it work?!


Issuing the following command seemed to confirm that there was no queuing strategy on the uplink port g0/1:

StrettonAv-A#sh queueing interface g0/1

Interface GigabitEthernet0/1 queueing strategy: none


Regards

Paul

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