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Community Member

Does a 3750 support cbwfq

We would like to implement Qos based on CBWFQ.

Does a 3750 with a ip base license (c3750x-24t-s) this?

Thanks in advance for your answers.

3 REPLIES
Cisco Employee

Does a 3750 support cbwfq

According to this its not supported yet.

http://www.cisco.com/en/US/customer/products/hw/switches/ps672/products_qanda_item09186a00800a8922.shtml#qa20

CBWFQ on this which is unfortunately _not_
supported on this platform irrespective of the IOS being used. So in


essence, there is no way to configure a policy-map with the priority nor
bandwidth commands. 
 
You can configure one ingress queue as the priority queue by using the mls
qos srr-queue input priority-queue  bandwidth  global
configuration command. The priority queue should be used for traffic (such
as voice) that requires guaranteed delivery because this queue is guaranteed
part of the bandwidth regardless of the load. 
 
SRR services the priority queue for its configured weight as specified by
the bandwidth keyword in the mls qos srr-queue input priority-queue
 bandwidth  global configuration command. Then, SRR shares
the remaining bandwidth with both ingress queues and services them as
specified by the weights configured with the mls qos srr-queue input
bandwidth   global configuration command. 
 
Each port supports four egress queues, one of which (queue 1) can be the
egress expedite queue. These queues are assigned to a queue-set. All traffic
exiting the switch flows through one of these four queues and is subjected
to a threshold based on the QoS label assigned to the packet. 
 
Only queuing and scheduling can be done on the egress which will not give
you the same results as policing.
 
Please do go through the configuration guide outlining the QoS capabilities
of this platform:
http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/1
2.2_44_se/configuration/guide/swqos.html
 
Please feel free to contact me in case you have any further queries.

HTH

Regards

Inayath

Community Member

Does a 3750 support cbwfq

When you have a look to this site:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/software/release/12.2_53_se/configuration/guide/swqos.html#wp1020443

You should think it is available. But only the needed license is not described.

Cisco Employee

Does a 3750 support cbwfq

Danny,

I do not believe CBWFQ will ever be supported on the Catalyst 3750 platform. The CBWFQ is  such a fancy queueing algorithm with so many degrees of freedom that it  is outspokenly difficult to implement it in hardware (as every  significant packet operation has to be implemented in hardware on  multilayer switches). The 3750 platform does not currently have such  hardware built in so CBWFQ can not come just with an IOS upgrade, and I doubt such hardware will ever be built into the Cat3750. To my best knowledge, CBWFQ was only available on high-end switch, such as Cat6500, on selected line cards.

Your link points to a documentation that explains the use of Modular QoS CLI, or MQC, to configure selected QoS features. However, that does not mean that CBWFQ is the mechanism behind the queueing. The Cat3750 supports SRR (Shaped/Shared Round Robin) only and you currently can not get any better.

Best regards,

Peter

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