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QOS configuration question

I have configured QOS on a cisco internet router using bandwidth statements. When the interface is fully utilised the interface allocates bandwidth according to the ratio of bandwidth statements configured. So for example if I have a 10Mbps internet connection with bandwidth 7000 allocated to Client A & bandwidth 3000 allocated to client B, when the interface is running at 10Mbps the utilisation should be split 70:30 (provided each client is sending enough traffic).

I can only apply the QOS in an outbound direction otherwise I receive the error "CBWFQ can only be applied on outbound interfaces". This means that I can only control inbound traffic by applying the service-policy in an outbound direction on the ethernet interface of the router.

Right, now my question. If the ethernet interface is 100Mbps, how will the interface know that it is overrun at 10Mbps and allocate 70:30 as per the bandwidth statements? Surely my only option can't be to configure the ethernet interface to 10Mbps??

Any help greatly appreciated.


Re: QOS configuration question

You need to create a artificial queue by limiting the interface. This is done with parent/child service policies.

You first create a policy (you can use class default if you want) and use the SHAPE option to limit the amount of traffic to 10m in your case.

Within that policy you put another service policy statement that uses your current service policy.

You then apply the shaping policy to the physical interface.

You should be able to use the default values in the shaping but if you are seeing unexpected loss you will need to have a discussion with your ISP about burst rates.

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