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Understanding - srr-queue bandwidth shape

Martin Houde
Level 1
Level 1

Hello folks,

 

I'm in a bind right now, I'm trying to shape traffic outbound on both sides of a link.

 

On one side, I have a Catalyst 9300 and on the other, I have a Catalyst 3750.

 

On the Catalyst 9300, I am using MQC (Modular QoS CLI) to shape traffic to a maximum of 70% of the outbound traffic, and on the Catalyst 3750 I am trying to do the same, however, I'm not sure how to do it on the Catalyst 3750 side...

 

What I'm looking to do is commandeer the Q1 on the 3750 by tagging/setting the DSCP of the traffic I want directed there to CoS5/DSCP46(EF) so that it takes Q1.  Q1 needs to be using 70% of the total bandwidth available MAX.  The rest of the traffic will be shared.

 

Here is what I'm using on the Catalyst 3750 side (I am not using Priority Queuing):

srr-queue bandwidth share 0 70 25 5

srr-queue bandwidth shape 2 0 0 0

 

 

 

I'm basing this on the configuration guide:

"Shaped or Shared bandwidth weights can be assigned to a queue via the srr-queue bandwidth shape and srr-queue bandwidth share interface commands. Shaped mode weights override shared mode weights and use an inverse ratio (1/weight) to determine the shaping bandwidth for the queue. Furthermore, if shaped weights are set to 0, then the queue is operating in shared mode. For example, the following interface command srr-queue bandwidth shape 3 0 0 0 would shape Q1 to 1/3 of the available bandwidth and set all other queues to operate in sharing mode."

 

Using the inverse ratio, how am I to get 70% bandwidth shaping for CoS5/DSCP EF ?

 

Thanks in advance,

Martin

1 Accepted Solution

Accepted Solutions

Hello,

 

the short answer is: you can't. If you configure '1' then you get 100%, if you configure '2' then you get 50%. Since you cannot use fractional values, 70% is not possible.

View solution in original post

2 Replies 2

Hello,

 

the short answer is: you can't. If you configure '1' then you get 100%, if you configure '2' then you get 50%. Since you cannot use fractional values, 70% is not possible.

As I suspected... I guess there are no work arounds with mathematics!

 

Thanks for help, it is much appreciated.

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