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New Member

Need help configuring QOS

Hi I need help configuring QOS on cisco 3750 switch. I was previously using 2950 and that needs replaced by these 3750 and the QOS configured on the new 3750.

Global configuration

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

mls qos

Interface configuration

interface FastEthernet1/0/1

switchport trunk encapsulation dot1q

switchport trunk native vlan 22

switchport mode trunk

switchport voice vlan 22

mls qos trust cos

storm-control broadcast level 10.00

spanning-tree portfast.

Now I didn't see any DSCP marking when I capture packets using ethereal


Re: Need help configuring QOS

There is nothing in your configuration to indicate that you have "attempted" to configure packet marking, queueing, or any of the other key aspects of QoS.

It "appears" as though you expect someone to do all the work for you.

You need to first define what your requirements are, before you can commence with QoS configuration.

I suggest you do a search on the Cisco web site for a document titled "Quality of Service Solutions Configuration Guide"; do some reading; define your requirements; and then return with a request for assistance following some initial attempts to configure QoS.

No offense intended.

Re: Need help configuring QOS

Check out the Enterprise QoS Design Guide here:

Very useful document - Paul

Re: Need help configuring QOS


Thanks for digging up the URL.

New Member

Re: Need help configuring QOS

I have a lot consideration on 3750 but no avail. I have configured the swtich as per the configuration given above. I didn't get the desired DSCP value on packets captured on ethereal. I have qos markings on the IP Phone and port is trusting on cos while the trunk is trusting on dscp and qos is globally enabled on the switch. I am able to capture packets with dscp values on the the earlier 2950 switches

New Member

Re: Need help configuring QOS

If I have trust qos dscp on trunk port and capture the traffic of this trunk will it has qos marking . Is qos marking on trunk while packets are entered/exit. Thanks

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