QoS on ATM subinterface

Unanswered Question


I am attempting to apply a simple CBWFQ/LLQ policy for voice traffic over an ATM UBR configured as a subinterface. When I apply the service-policy to the PVC on the subinterface it doesn't stick. A warning is logged saying that there is no available bandwidth to reserve. From other reading it seems this is directly related to PVC being configured as a UBR. Does this mean no QoS can be applied to a UBR? If not, then how must this be done?

Here is a sanitized snippet of the config in question:

policy-map QoS-WAN

class VoIP-Voice

priority 768

class VoIP-Control

bandwidth 16

class Critical

bandwidth 256

class class-default



interface ATMx/x.x point-to-point

bandwidth 10000

ip address x.x.x.1

pvc 1/x

protocol ip x.x.x.2 broadcast

ubr 10000

encapsulation aal5snap



Thanks in advance,


I have this problem too.
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rkhalil Wed, 07/30/2008 - 12:36

The policy is accepted on an ATM VC since the VC supports native ATM-layer shaping via the vbr-nrt, vbr-rt, cbr or abr commands.

I thinks the service-policy on ubr vc not works..

but try..

(config)#int atm x/x.x

config-subif)#pvc x/x


(config-subif)#service-policy output QoS-WAN




Thanks for the response. I cannot apply the service-policy to the subinterface directly. When attempted I receive the following:

CBWFQ : Not supported on subinterfaces

To clarify, when I apply the service-policy to the PVC it accepts the command initially but reports the following when exiting config mode.

Jul 30 14:43:49.433: I/f ATMx/x.x VC x/x class VoIP-Voice requested bandwidth 0 (kbps), available

only 0 (kbps)


rkhalil Thu, 07/31/2008 - 08:00

Try configuring Class-Based shaping..

policy-map TEST

class dscp46

shape average 30000 10000

class web

shape average 20000 15440


(config)#int atm x/x.x

config-subif)#pvc x/x


(config-subif)#service-policy output TEST




I configured the following:

class-map match-all GENERAL_TRAFFIC

match ip dscp default

policy-map SHAPE-WAN-ATM


shape average 9000000 256000

When I applied it to the ATM subinterface I recieved the following:

GTS : Not supported on this interface

I tried applying it to the PVC as well and it initially took but reported the following when exiting config mode:

Jul 31 11:29:51.750: GTS : Not supported over ATM VCs

Any other thoughts?

Giuseppe Larosa Sat, 08/02/2008 - 12:49

Hello Jim,

try to apply the command to the physical interface

What happens ?

May you tell what router model, ATM interface and IOS version you are using

Hope to help


Giuseppe Larosa Sun, 08/03/2008 - 22:09

Hello Jim,

you are right: you are using a powerful router but of course you cannot apply the service-policy on the physical interface if you have other 20 PVCs and subifs working.

I just wanted to understand the scenario.

If you have been able to apply service-policy on other ATM subinterfaces and/or PVCs that are not using UBR, the only way is to change the ATM Class of service of this PVC, because the IOS checks if the PVC has some guaranteed resources or not (like it happens for UBR).

Try to negotiate with the service provider a change in the ATM CoS of the PVC or configure it as an ABR with low parameters just to be able to apply the service-policy (I'm not sure that this is without drawbacks so verify if there are )

Hope to help



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