QoS for Voice Traffic

[harish.singh.g]

Hi All,

I would like to know how do I configure QoS for Voice Traffic.

In our network we have configured multiple ports under one voice vlan. I would like to configure QoS on these ports.

Also please let me know whether can we configure QoS for the Vlan configured for Voice.

Regards,

Harish

[jonathanaxford]

Hi Harish,

What model of switch are you using?

I would recommend that you look into using "Auto QoS" - this offers a simple to setup QoS policy and works well for most implementations.

It basically runs a whole series of commands that enables QoS globally on your switch and also on the ports that you specify the command on.

If you identify what switch models you are working with, the associated Cisco config guides should be able to get you started. In terms of QoS for the VLAN - QoS is enabled on the physcial switchports as it is used to control the flow of traffic into and out of the port itself - you can enable QoS for all ports within a specific VLAN, you don't have to have all ports setup for QoS.

Hope this helps a little,

Jonathan

[Latchum Naidu]

Hi Harish,

Please see the below link for your requirement.
http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_19_ea1/configuration/guide/swvoip.pdf

It clearly specify step by step config for voice vlan and qos also.

Hope this will helps you.

Please rate the helpfull posts...
Regards,
Naidu.

[harish.singh.g]

Hi Naidu,

First of all thanks for the link.

After referring to the links, I have a few doubts:

1. How am I supposed to know that the my switch supports both 802.1q or 802.1p for voice traffic.

2. According to the following examples:

Example 1: Does the following example relay that the voice traffic will be preferred over data traffic if the CoS priority is set to greater than 0 (or) is it the data traffic being preferred the most.

mls qos
!
interface fa0/30
mls qos trust cos
switchport access vlan 10
switchport voice vlan 7
switchport priority extend cos 5

Example 2: Hope the below example is for trusting the data traffic over the same interface.

mls qos
!
interface fa0/30
mls qos trust cos
switchport access vlan 10
switchport voice vlan 7
switchport priority extend trust

[harish.singh.g]

Hi Jonathan,

We are using 2950, 2960, 3550, 3750 for access switches. The Voice Vlan's are configured in 4507/6506 switches.

We are using Avaya & Nortel IP phones.

Also you have mentioned that:

"you can enable QoS for all ports within a specific VLAN, you don't have to have all ports setup for QoS"

Does the above statement apply for a Vlan configured in the same switch where the ports reside

or

you can configure QoS in a Vlan and all the ports irrespective of the switches will be supported.

Hope I am clear.

Regards,

Harish

[jonathanaxford · Accepted solution]

Hi Harish,

I am not quite sure wha you mean. As a basic principle, you will need to enable QoS on each switchport that connects to an IP Phone and to each trunk port that connects to another switch. This ensures that your QoS markings are carried/trusted throughout your network. As far as I know, you cannot enable QoS on a VLAN basis - you must do it for the physical ports.

There are certain things that you need to decide, such a whether to trust CoS or DSCP Values (I'd recommend DSCP where possible). QoS can be complicated to get your head around, I would recommend spending some time reading through some config guides and articles to help get a clearer picture of what you wish to achieve. I am sure that Avaya have some documentation on running their telephones on a Cisco LAN too, so it might be worth looking at that too.

Many thanks

Jonathan

[harish.singh.g]

Hi Jonathan,

Thanks for the info. Will let u know if I face any issues while implementing QoS.

If possible kindly refer a few config guides for QoS.

Thanks in advance.

Regards,

Harish