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GTS on the ISR router

Hi friends,

Two things to ask here:

A) I tried a lot to find the answer to this on the cisco website but couldnt track it anywhere so far.

Basically wanted to confirm if i could use GTS on 1921 routers? It seems it doesnt support it cos when i was trying to run the command on the g0/1 interface of the router, it did not like "tarffic-shape" keyword at all. I could only see "rate-limit" (CAR) as the option available.

I am still new to these concepts and all I wanted to achieve was to set my outbound speed to 6 Mbps as thats what the ISP is providing me.

B) I was advised that GTS was the simplest option to choose from, but when I realized that the router wasnt liking it, I thought of using CAR but then wasnt able to understand the best value for burst size and excess burst size that i should use.

I read on the cisco website that they recommend the following formula,

normal burst= configured rate * (1 byte)/ (8 bits) * 1.5 sec

excess burst = 2 * normal burst

But honestly, i did not follow this properly to decide what value should i use?

Thanks in advance!



Everyone's tags (3)
Hall of Fame Expert

Re: GTS on the ISR router

Hello Mohit,

CAR is not a replacement for GTS it uses policing instead of shaping

Shaping delays traffic in excess of the committed rate, policing drops traffic in excess. So CAR is much more intrunsive on traffic.

In modern routers you can achieve the equivalent of GTS using modular QoS

policy-map SHAPE-6Mbps

class class-default

shape average 6000000

interface type x/y

description your WAN interface to provider

service-policy SHAPE-6Mbps output

you can check the operations of the policy-map with

show policy-map interface

Hope to help



GTS on the ISR router

Hi Giuseppe

Thanks for replying -after your suggestion, I read about the Modular QoS and realised that there was an option “bandwidth” that I could use in the class-map config mode. Wouldn’t you reckon that would be better if my intent is to set the bandwidth on the interface?



VIP Expert

GTS on the ISR router


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The CBWFQ bandwidth statement, in non-LLQ classes sets a minimum value.  What Giuseppe suggested would be the GTS equivalent.


GTS on the ISR router

Alright then, I'll try to use this on my router and let you know once i am done.


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