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Earl Kacin

QOS for c2960-48pst-s with ios 12.2 (50) SE3

There are is no "auto qos voip" macros on this switch.  Does nayone know what the commands are for setting up qos on these switches?  I treid to copy the qos lines from another 2960 with the qos lines already in the config, but they dont all seem to be included in the ios. Do I need to upgrad the ios of the switches? It didnt accept all of them. Anyones help would be appreciated.



The 'auto qos' command is basically a trigger for a macro that applies all the other qos commands that appear after you've entered it. You have two options:

1) Read the QOS configuration guides for the version that accepts 'auto qos', and the version that doesn't, and work out the correct commands to parody what the new version does without applying the 'auto qos' commands. It may not be much different to copying everything except 'auto qos' commands accross.

2) Just upgrade the switches to consistent IOS for consistent behaviour.

Second option should be more reliable and easier. I'd read the books anyways.



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Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
Jason Pennell

Hi Earl,

I had this same question when I had to configure my first 2960 switch running on the LAN Lite image (VS LAN Base image).  The problem is that the LAN Lite image has a very limited QoS feature set and unfortunately it is not just a matter of upgrading to a LAN Base image.  You can't upgrade a LAN Lite to a LAN Base or downgrade a LAN Base to a LAN Lite.  It is just the way the switches are built. 

Anyway, I tried reading through different QoS documents and even opened a TAC case on the matter.  The below example is what I came up with.  My installations are more focused on the QoS being able to support Cisco IP Phones in the network so the below example may not apply to all scenarios, and I'm not sure it is 100% accurate but it is based on the information I've read and the information I received back from TAC.  It is also what I've been deploying on my 2960 LAN Lite switches and I've not had any issues with it yet. 

In global config enter the following commands...

! Enable QoS globally

mls qos

! Map CoS values 0-7 to the queues and thresholds.  These configs are taken from the Auto QoS script run on a LAN Base 2960 switch

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 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

! Disable the switch from rewriting DSCP.  Since there is no ability in these switches to create your own CoS to DSCP mappings you have to use the default map which takes each CoS value and multiplies it by 8.  So CoS 0 maps to DSCP 0 and CoS 1 maps to DSCP 8, and CoS 2 maps to DSCP 16, and so on.  That means that CoS 5 used for voice maps to DSCP 40 instead of DSCP 46 (EF) like it should map to.  With the below command the DSCP value will never be rewritten so when an IP phone sends a packet marked with CoS 5 and DSCP 46 it will be trusted and not overwritten to DSCP 40. 

no mls qos rewrite ip dscp

On the interfaces you want to enable QoS on, use the following commands..

! Trust the CoS settings coming in from the switch.  It is unfortunate that you cannot enable conditional trust when an IP phone is attached like you can in a LAN Base image with the mls qos trust cisco-phone command.  Instead you can use the command below which trusts any CoS coming in on the port from whatever device that is attached.

mls qos trust cos

! Configure the inteface priority queue.  CoS 5 is mapped to queue 1 and queue 1 is the priority which allows all CoS 5 traffifc to be serviced first. 

priority-queue out

Some good docs to reference to understand QoS better and perhaps build upon/tweak this configuration are...

2960 Configuration Guide QoS section -

Medianet QoS Campus Design 4.0

I hope this helps you out. 

Good luck.

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