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allocate bandwidth for voice on 3750 for a wan connection

3M WAN link(from LAN extension service) is connected between 3750 switch fast ethernet and 6509 fast port.Tring to allocate 1M for voice on 3750. My consideration is that it seems 3750 allocates bandwidth based on the port speed using srr command. In my case the port is 100M, but real bandwidth is 3M. How can I do this? Can I design the wan like this or have to use router to avoid this problem?

3 REPLIES
Bronze

Re: allocate bandwidth for voice on 3750 for a wan connection

CBWFQ

CBWFQ extends standard WFQ to provide support for user-defined traffic classes. For CBWFQ, users define traffic classes based on match criteria, including CoS, IP Precedence, IP DSCP, and MPLS EXP bits. Packets satisfying the match criteria for a class constitute the traffic for that class. A queue is reserved for each class, and traffic belonging to a class is directed to the queue for that class. After a class has been defined according to its match criteria, users can assign it bandwidth to guarantee a minimum amount of bandwidth that is available to it during times of congestion.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800b75af.html#1041636

New Member

Re: allocate bandwidth for voice on 3750 for a wan connection

Use the bandwidth command on the interface for QoS to use .. bandwidth 1024 (K) tells it that 1Meg is available.

Re: allocate bandwidth for voice on 3750 for a wan connection

Hello,

the qos capabilities of the Catalyst 3750 are described in "Configuring QoS" at

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_guide_chapter09186a00802c1100.html

It states about the Expedite Ingress Queue for VoIP:

"High-priority user traffic such as differentiated services (DF) expedited forwarding or voice traffic. You can configure the bandwidth required for this traffic as a percentage of the total stack traffic by using the mls qos srr-queue input priority-queue global configuration command. The expedite queue has guaranteed bandwidth."

And on output:

"If the expedite queue is enabled, SRR services it until it is empty before servicing the other three queues. "

This sounds to me like your requirements can not be met. What you would need is called nested policy and afaik only available on routers.

Have a look at "Traffic Policy as a QoS Policy (Hierarchical Traffic Policies) Example"

http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a00800bd909.html#1022062

for an explanation and configuration example.

Hope this helps! Please rate all posts.

Regards, Martin

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