QoS for Voice and Data

Unanswered Question
May 25th, 2009

I am working on WS-C3750G-12S and WS-C3750G-12S. 2960 has an IP phone connected to its fa 0/48 interface. So I did

Int fa 0/48

mls qos trust dscp

Then I created a class-map

class-map VOIP_RTP

match ip dscp 46


match ip dscp 26

Then I created a policy-map

Policy-map QoS

class VOIP_RTP

switch2960(config-pmap-c)# ?

QoS policy-map class configuration commands:

police Police

set Set QoS values

trust Set trust value for the class

The first problem here is that it doesn't give me an option to set priority or bandwidth

Anyhow, I did set dscp here as well.

Policy-map QoS

class VOIP_RTP

set dscp 46


set dscp 26

Now When I tried using the policy on the outside interface (the interface that connects to a 3750) it doesn't allow me to use the policy in outbound direction.

switch2960(config-if)#service-policy output QoS

Warning: Assigning a policy map to the output side of an interface not supported

Service Policy attachment failed

Warning: Assigning a policy map to the output side of an interface not supported

Could someone please help me in applying QoS in this scenario.


I would be very great full.


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James Hawkins Thu, 06/04/2009 - 03:03

I think that maybe you are trying to apply router based IOS commands to a switch. This is not supported as switches have special commands to set bandwidth etc.

For example to allocate bandwidth to queues on a 2950 port you use the command below:

wrr-queue bandwidth 5 25 70 0

The four values set the relative bandwidths of the four queues available to the switch.

The link below shows how to configure QoS for the 2950 in various scenarios.


One tip that may be helpful is to start off using autoqos and modifying what that sets up to meet your specific needs.

Please rate if helpful.


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