Switch Qos

[bmurray]

I have 2 Cisco 3560 switches trunked to each other. I have the following on both trunk interfaces. It is a point to point 10 meg link with a non

Cisco voip solution. There are 2 san devices at both sites trying to replicate data and when more than one replication happens the phone

quality breaks up.

interface GigabitEthernet0/23

description ***TW Trunk to 3560G Port 3 P2P****

switchport trunk encapsulation dot1q

switchport mode trunk

switchport nonegotiate

srr-queue bandwidth share 1 30 35 5

srr-queue bandwidth shape 10 0 0 0

priority-queue out

mls qos trust cos

auto qos trust

[Mohamed Sobair]

Hello,

Your Config Looks Ok, except for the bandwidth share command as its not in effect as long as you have (bandwidth shape) configured on the interface. The Bandwidth shape command has precedence over it, and treats all other queues whic set to 0 value to be in a shared percentage. so you dont need it, you can remove it from the configuration.

Try to make sure your Phones on the Access Ports are set with the right QoS - CoS value, and there is a proper QoS configuration on the Access ports as well.

Regards,

Mohamed

[Joseph W. Doherty]

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Posting

Have you confirmed your VoIP and SAN replication traffic is correctly marked and getting into the correct queues?

You do this in both directions?

Have you checked for any other potential bottlenecks?

[bmurray]

What are the best ways to verify qos tagging and operation?

Sent from Cisco Technical Support iPad App

[Mohamed Sobair]

Queue (1) is the priority Queue on your Switch, a CoS value of 5 should automatically be mapped to this queue.

To make sure your phones sets the right QoS - CoS value, you may use a network tester before even pluggin the IP-Phone to the Switch Port. On the Switch side, there is no specific command can reveal the CoS Value Sets on your phones.

If you are having difficulty getting a Tester, You Can Just Set all Access Ports on the Switch with the Proper CoS Value (5) where your Phones are connected and you should not experience such drop after that.

The Command On the Catalyst Switch is:

Interface G0/1

mls QoS CoS 5

priority-queue out

Like wise, it should be set for all Access Ports where the Phones are connected, notice, also the priority queue is set. This will make sure you have Classification and Marking at the Access and Proper QoS treatment from the Access to the Uplink where als the CoS value are trusted.

HTH

Mohamed

[singhaam007]

hello,

Qos is not easy to understand and it can get more confusing if you change its default behaviour.

All cisco phones mark there traffic with COS 5 and it get change into DSCP 46 at layer 3.

Please see this document for more detail information.

Please rate if this helps

thanks

[Peter Paluch]

Hi Amrinder,

Hey, that's a nice document! Did you write it yourself?

Apart from this, there is a good discussion and a fine in-depth document posted on CSC here:

https://supportforums.cisco.com/thread/2051188

https://supportforums.cisco.com/docs/DOC-8093

Best regards,

Peter

[singhaam007]

Hi Peter,

thanks mate.

i got it from my work mate. just keeping it on my hard drive coz its really good.

i am still learning.

but i will write one soon with some more details.

thanks so much for the links.

cheers