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QoS and IP phones

Hello guys,

Since I didn't see QoS section in the forum I am posting here.

I have one Cisco 3560 connected to a Cisco 2960. We have all our IP hard phones (Avaya)connected to a Cisco 2960 switch. When I check the option on the phones I see the phone marks the traffic with DSCP 46 for Audio and DSCP 34 for signaling. I implemented the following access list to the Cisco 3560 (the switch above the 2960) to capture the marking from the phones:

Extended IP access list 102

10 permit ip any dscp ef

20 permit ip any dscp af41

30 permit ip any dscp af31

40 permit ip any any (15 matches)

As you may see I am catching only any any conversation matching. Is it possible Cisco 2960 removing the DSCP marking from the phones on their way to the upper switch 3560 Switch?

Thanks in advance!



Re: QoS and IP phones

There is a couple things to consider..

1.) IF qos is enabled on the 2960 switch and you do not have the individual ports set to trust the marking of the device, then all packets will be marked as BE (Best Effort).

2.) If you have not enabled QoS 2960 switch, but on the 3560, then On the 3560 switch that is uplink to the 2960 switch you need to trust dscp markings coming from the 2960. Otherwise, the packets will again be marked as BE as they pass from the 2960 to the 3560.

The 2960 unless activated with mls qos, will act as a passthrough switch.

So in your case, I would go ahead enable qos on teh 2960. Create the same access-list. Apply it to a qos policy and apply it to all ports with phones. On the uplink ports configure it to trust DSCP markings. Both going out of the 2960 and in to the 3560.

This at least gives you some idea.

I hope this helps, if so please rate post.

Community Member

Re: QoS and IP phones

It is helpfull. The QoS is not enabled on both 2960 and 3560, and it won't be in the future. I just want to know if the 2960 is able to remove DSCP set by the IP hones? Is there a better way to see if the phone are marking then the access list above?


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