3845 router Modular QOS on ATM sub-interface

Unanswered Question
Dec 29th, 2008

Hi All,

We were trying to configure Modular QOS on an ATM sub-interface in output direction on a Cisco 3845 router and we get an error message stating CBWFQ not supported on sub-interfaces.The sample config as below

policy-map x

class w

priority percent 20

class y

bandwidth percent 10

We have class-map configured appropriately.

Any help would be appreciated.



Anantha Subramanian Natarajan

I have this problem too.
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Joseph W. Doherty Tue, 12/30/2008 - 05:45

QoS will need to "know" the bandwidth of the subinterface to accept the QoS service policy.

(I've often worked with ATM vbr-nrt PVCs that define the subinterface's bandwidth and support a service policy in the subinterface's PVC section.)

anasubra_2 Tue, 12/30/2008 - 06:01

Hi Josephdoherty,

Thanks for the response.... Actually we tried to configure the service-policy under the PVC statement on that subif and also the router takes that config but it doesn't show in the config.

Any idea on that

Thank you


Anantha Subramanian Natarajan

Joseph W. Doherty Tue, 12/30/2008 - 12:44

Can't say for sure in your case, but I have seen service policies appear to be accepted but not show in the config if they have explicit bandwidths that are more than the interface supports. If you apply the policy from a telnet connection you won't see an error although I've seen the error appear on the console and router log.

In your sample, though, you're using percentages and this should avoid the issue I just described.


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