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QOS issue or some thing else


PLease find the below config, why is it taking the interface bandwidth 100Mbps instead of the Bandwidth of the link 70 Mbps.Please find the attached config.

7 Replies 7

Mohamed Sobair
Rising star
Rising star


you can only reserve 75% of 70Mbps, your QoS config shows you have reserved 100% of the 70Mbps configured bandwidth.

It shouldnt be, unless you have (max-reserved-bandwidth 100) configured at the interface?

Could you please post all QoS related config?



Seems a bit strange

What is the platform and the IOS version/module you are using?

Can you remove the service-policy and then add it again along with the max-reserved-bandwidth 100 command and see whether it rectfies?


Bit strange for me too. Its 1200 GSR router.

This is the all config i can post,The default class has the 70% bandwidth allocation.but in the sh policy-may it is using the int bandwidth.which config part is showing the 100% of 70Mbps

Joseph W. Doherty
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

I see your issue is you're hoping QoS will derive it's bandwidth percentages based on the interface's bandwidth statement (70 Mbps) rather than the interface's physical bandwidth (100 Mbps). I'm unsure whether that's a correct assumption since QoS, for actual queue bandwidth allocations, relies on actual congestion and that would only happen when the interface congests at 100 Mbps. But assuming it did use the bandwidth statement (which is might for other platforms and/or IOS versions), it shouldn't really make much of a difference since CBWFQ really uses class bandwidth for assigning queue weights. Of course the bandwidth allocation can be extremely important if some traffic really requires an actual amount of bandwidth, but then you would be better served by using absolute bandwidth rather than percent bandwidth or you'll need to adjust such percentages everytime the interface bandwidth varies.


What should set the bandwidth percentages to your values you expect, and might be even more imporant if the path is limited to 70 Mbps further downstream, would be to use a top level shaper configured for 70 Mbps and your policy subordinate to it.

If u can demonstrate giving some config example taking the reference of the current scenario

policy-map shape70M

class class-default

shape average 70000000

service-policy ABHAY

interface FastEthernet0/1/0

service-policy output shape70M



The shaper might not allow for L2 overhead, so you might actually need to shape a little slower, somewhere between 5 to 15% slower (depends on you average packet size). I find 10% slower a good starting point, i.e.

policy-map shape70M

class class-default

shape average 63000000

service-policy ABHAY

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