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VoIP and QoS

Hoping someone will be able to assist as I have 3 stacked 3750x switches that need to be configured for VoIP and will require QoS for both the voice and video configured. 

To start with I think that the VoIP configuration that will work is as follows - the phones are Alcatel-Lucent not Cisco;

Switch mode encapsulation dot1q

Switch mode dynamic des

switch trunk native 2

switch trunk allowed 2, 102

speed auto

What the end game here is to have the ports in a state that will allow a static connection for printers etc but for phones enable the trunk and tag the appropriate vlan. 

Where it all comes unstuck is with the QoS, the Alcatel system flags the packets at the phone and none of the network devices have a QoS "map" for it.  The VC does not tag the packets and relies on the switches and routers to have a "map" for the priority.

My understanding of QoS is rather rudimentary (non-existent) and the documentation on the Cisco site has not enlightened me very much. 

Would someone be able to walk me through reverse engineering the existing setup and how to recreate this in a more logical way?

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Re: VoIP and QoS

Your phones are in VLAN 102 and the computers, printers (which can't tag the packets) are in VLAN 2, is that right?

Do the alcatel phones have the ability to mark packets?

If yes, following are the cisco recommended options L2 audio- 5, L2 signaling- 3  and L3 audio- 46, L3 signaling- 26.

If not, you can match the packets based on the IP range (access-list).

for the video conferencing units you can match the packets based the port ranges and ip addresses below is the example

access-list 150 remark QoS Video conference

accessl-list 150 permit udp any any range 2326 2487

access-list 150 ip any 10.24.0.0 0.0.255.255

Then you can create a policy-map to mark the packets that leaves your CE router.

QoS is a end to end configuration your service provider should respect your markings otherwise packets will lose their markings when they levae that router.

Below is a very good document that explains the QoS config on the 3750 switches

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a0080883f9e.shtml

Siddhartha
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