QoS basics 3560 layer 3 switch

Unanswered Question
Jun 3rd, 2008

I have a 3560 layer 3 switch that has polycom voip phones and workstations connected to it

The network is partitioned into vlans but the polycom voip phones and workstations reside on the same vlan

I would like to implement QoS on an interface basis and give the voice packet priority

For the time being we do not have any plans to create a voice vlan just for the phones since we do not have a lot of voip phones but the requirement for QoS is very urgent.

I'm looking for a basic QoS setup that will give the voice traffic priority

I have just globally enabled mls qos on the switch and looked at some interface configuration options but I'm not sure which one to use with respect to the most common settings when using non Cisco gear and I'm not sure if I need to configure any outgoing queues or if the default queue is fine.

I'm looking for a basic configuration example on interface g0/10 one vlan both voip and desktop connect to g0/10 voip device is non-cisco

A link on QoS would also be helpful to reinforce the example provided and education on other types of examples

Thank you,

JR

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Ryan Carretta Tue, 06/03/2008 - 11:37

The quick and easy way to get you on your feet will be to use auto-qos. Here is a doc on that on 12.2(44)SE:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_44_se/configuration/guide/swqos.html#wp1231112

You should be able to just globally enable 'mls qos' and then on the interfaces connecting to the phones, and the interfaces connecting to the network interior enable 'auto qos voip trust'.

Make sure that qos is also enabled on the transit devices, and that they are trusting the relevant tags (cos for layer-2 links, dscp for layer-3).

Let me know how it goes. =)

juan-ruiz Tue, 06/03/2008 - 12:39

Hi rcarrett,

Thanks for your info. So I understand your message this is what I'm planning on doing

mls qos globally on the switch and on the interfaces that connect to the voip phone auto qos voip trust and on transit devices which if I understand right is the voip phone enable qos

Please correct me if I'm wrong

If I have downstream switches I would also enable on those trunks auto qos voip trust too

Thank you

JR

andrew.butterworth Tue, 06/03/2008 - 13:12

Be aware that enabling QoS on a 3560/3750 sets up four egress queues per interface, each of which gets 25% of the scheduler. Queue One is also by default shaped to 25% and by default CoS-5 & DSCP 46 Map to this queue (usually what RTP frames are marked with). This is usually fine on a single VoIP call (i.e. attached to an IP Phone) but if it's a link that aggregates multiple VoIP calls it may cause problems. I am not sure if the latest code enables the strict-priority queue with Auto-QoS, but it didn't when I last looked at it. Personally I wouldn't use Auto-QoS, however it's your choice.

I suggest you have a read of the QoS SRND as this has example configs you can use as a base for most switch types:

http://www.cisco.com/go/srnd

Andy

juan-ruiz Wed, 06/04/2008 - 09:58

Everyone thank you very much for the participation.

Last but not least using the auto QoS only affects the interfaces I configure it on so I could enable it on interfaces that voip phones connect to and not enable it on trunk interfaces

Would that work until I understand the deployment technology more?

This is what I got when I enabled auto qos on interface g0/10 as my first test interface

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 queue-set output 2 buffers 16 6 17 61

andrew.butterworth Wed, 06/04/2008 - 10:26

When you enable QoS globally queueing is enabled on all interfaces, this is not configurable on a per-interface basis. You can enable the 'trust' state per-interface, however the egress queueing is derived from the QoS value (CoS or DSCP) of the frame to be transmitted.

Andy

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