Posted on October 8, 2021 6:57 pm
 |  Asked by Bengi Karacali-Akyamac
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Could you share information/documentation about expected behavior with the QoS option “bandwidth guaranteed” configuration, beyond the user guide QoS section? Specifically, what happens when the traffic mapped to the queue with “bandwidth guaranteed” configuration exceeds the specified bandwidth?

Posted by Akshita
Answered on October 11, 2021 9:38 am
The guaranteed bandwidth feature provides/ allocates required bandwidth for the outgoing lower priority traffic from the specific queues to avoid their starvation. Below mentioned is the sample configuration:-
device(config)#interface et1
device(config-if-Et1)#tx-queue 2
device (config-if-Et1-txq-2)#bandwidth guaranteed 200 pps
Could you please let us know the hardware platform, EOS version as well as the exact configuration ("show running-config") which is being used/that you intend to use to implement guaranteed bandwidth.
Thanks and Regards
Akshita and Sandhiya
Answered on October 11, 2021 5:41 pm

Dear Akshita and Sandhiya,

Thank you for your answer.

Seems like, in your example,  allocating  200pps on tx-queue 2 configured with SP, makes sure that traffic from SP queues tx-queue 3 through 7 do not starve tx-queue 2. Similarly, tx-queues 0 and 1 configured with  SP must have a guaranteed bandwidth allocation in order not to be starved by the other  higher queues (2 through 7).
Is this correct?

Thank you and Best,


Posted by Akshita
Answered on October 12, 2021 11:51 am

Hi Bengi,


Yes, your understanding is correct. Tx-queue 2 is a lower priority queue due to which it can suffer starvation. The command "bandwidth guaranteed" is mostly used when the scheduling algorithm is "strict priority" for these queues. Since tx-queue 2 is of lower priority as, the guaranteed bandwidth makes sure to allocate specific/required bandwidth of this queue to prevent starvation by the higher priority queues. The same will be applicable for tx-queue 1 and 0 as well.


Thanks and Regards


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