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How to configure VOIP on 3750 switches.

Hi,

I am planning to configure my 1st VOIP installation using 2 3750 switches stacked togather and 3rd switch linked up via SFP Gigabit link. I have planned to use 5 vlans. The total users are 70 and this is a stand alone site.

For IPT phones and servers, my customer is using an external supplier to provide and install Voice servers and VOIP phoes. All voice hardware is MITEL make. I am not involved in Voice but i need to ensure the 3750's are configured correctly to work with Voice. I need your help as this is going live over the weekend. I have managed to speak to someone from MITEL and he provided me following guidelines:=

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In order to make the QoS settings work, the following points need to be considered:

1 QoS must be enabled for the entire switch.

2 The default COS and DSCP settings of the switch may not be those needed for voice.

3 Settings that are needed include:

- Change mapping COS 5 to DSCP of 46 (Expedited Forwarding (EF) setting).

- Ensure that COS 5 is mapped to the EF queue.

- Enable the EF queue.

- Trust incoming ports based on COS value for end points, phones, 3300 ICP and voice

servers.

- PC phones may require DSCP remapping as well as DSCP to COS conversion.

- Enable CDP.

4 Auto-qos trust will change a number of these settings.

5 Some additional tuning may be needed to the settings to get full operation.

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I have read the latest software configuration guide for Cisco 3750 but still unsure about the above 5 points.

I will really appreciate if someone can post relevant config parts specific to my case, an interface configuration to link MITEL IP3300 Voice Server as well as an interface configuration to connect MITEL phone.

I am ok with regards to VLANs, intervaln routing and standard data links as I have done this in the past with another customer using 2950, 2960 and 3560 switches but confused with VOIP, COS, DSCP and MLS parts.

I don't thonk I will need to do any policing as VOICE calls will not hit the WAN Router. But please put me right if i am wrong here..

Thank you in advance

Shaheen

2 REPLIES
Silver

Re: How to configure VOIP on 3750 switches.

The voice VLAN feature enables access ports to carry IP voice traffic from an IP phone. When the switch is connected to a Cisco 7960 IP Phone, the phone sends voice traffic with Layer 3 IP precedence and Layer 2 class of service (CoS) values, which are both set to 5 by default. Because the sound quality of an IP phone call can deteriorate if the data is unevenly sent, the switch supports quality of service (QoS) based on IEEE 802.1p CoS.

For More information please click following URL:

http://www.cisco.com/en/US/products/hw/switches/ps4324/products_configuration_example09186a0080722cdb.shtml

Re: How to configure VOIP on 3750 switches.

Here's a sample config i used in my network with 3750's

------Global configuration-----

mls qos

!

mls qos map cos-dscp 0 8 18 26 34 46 48 56

!

mls qos srr-queue output cos-map queue 1 threshold 3 5

mls qos srr-queue output cos-map queue 2 threshold 3 6 7

mls qos srr-queue output cos-map queue 2 threshold 2 3

mls qos srr-queue output cos-map queue 2 threshold 1 4

mls qos srr-queue output cos-map queue 3 threshold 3 2

mls qos srr-queue output cos-map queue 4 threshold 3 0

mls qos srr-queue output cos-map queue 4 threshold 1 1

!

mls qos srr-queue output dscp-map queue 1 threshold 3 46 40

mls qos srr-queue output dscp-map queue 2 threshold 3 48 56

mls qos srr-queue output dscp-map queue 2 threshold 2 24 26 28 30

mls qos srr-queue output dscp-map queue 2 threshold 1 32 34 36 38

mls qos srr-queue output dscp-map queue 3 threshold 3 16 18 20 22

mls qos srr-queue output dscp-map queue 4 threshold 3 0

mls qos srr-queue output dscp-map queue 4 threshold 1 8 10

mls qos queue-set output 1 threshold 2 75 85 100 400

mls qos queue-set output 1 threshold 4 15 100 50 400

On all the interfaces

mls qos trust dscp

queue-set 1

srr-queue bandwidth share 1 39 24 37

srr-queue bandwidth shape 5 0 0 0

priority-queue out

HTH, rate if it does

Narayan

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