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Beginner

Default QoS Behavior on Catalyst 3650/3850 Running IOS XE 16.3.6

I am trying to better understand the default queuing behavior on Catalyst 3650/3860 running IOS XE 16.3.6 Denali.

  1. Is QoS enabled globally by default? Coming from working with Catalyst 2960X on IOS 15 I am familiar with the mls qos global configuration and the show mls qos command to determine status. I am having difficulty finding the analogous commands in IOS XE.
  2. Assuming an "out of the box" configuration on the above captioned hardware and IOS, what would be the behavior of IP packets with DSCP markings? Example: end devices are marking DSCP 46, 34, and 26 for three different traffic types respectively. Without service policies will these packets be treated differently than any other traffic?
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VIP Advisor

Re: Default QoS Behavior on Catalyst 3650/3850 Running IOS XE 16.3.6

Hello again,

I think the commands you are after will be under:

 

show platform software fed switch qos

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-3/command_reference/b_163_consolidated_3850_cr/b_163_consolidated_3850_cr_chapter_01101.html#id_22277

 

Regarding the out of the box default behaviour the 3850 will trust the DSCP markings that it receives, but I believe the default queuing will not prioritise those packets over say the scavenger class. For thay you need to define your own policy maps or use auto-QOS.

 

cheers,

Seb.

3 REPLIES 3
VIP Advisor

Re: Default QoS Behavior on Catalyst 3650/3850 Running IOS XE 16.3.6

Hi there,

Take a look at this document, it will show you the comparative commands between the platforms:

https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3850-series-switches/118629-technote-qos-00.html

 

On the 3850 QoS is enabled by default. I don't have one to hand to check for you but I believe the default settings should give equal priority to all queues.

 

cheers,

Seb.

 

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-3/configuration_guide/b_163_consolidated_3850_cg/b_163_consolidated_3850_cg_chapter_01010010.html#reference_BDD017224E7B474FBCC967122032458C

Beginner

Re: Default QoS Behavior on Catalyst 3650/3850 Running IOS XE 16.3.6

Thanks Seb, I have reviewed the above captioned documents. Pardon my ignorance when it comes to QoS but I have two follow up questions:

1) When attempting any "show platform qos..." at the "qos" part I get "unrecognized command" - I know there have been some tweaks to syntax in newer versions of IOS XE. Do you happen to know what I might be doing wrong?

2) Can you elaborate on your statement "I believe the default settings should give equal priority to all queues" as it pertains to part 2 of my original question.

Thank you!

VIP Advisor

Re: Default QoS Behavior on Catalyst 3650/3850 Running IOS XE 16.3.6

Hello again,

I think the commands you are after will be under:

 

show platform software fed switch qos

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-3/command_reference/b_163_consolidated_3850_cr/b_163_consolidated_3850_cr_chapter_01101.html#id_22277

 

Regarding the out of the box default behaviour the 3850 will trust the DSCP markings that it receives, but I believe the default queuing will not prioritise those packets over say the scavenger class. For thay you need to define your own policy maps or use auto-QOS.

 

cheers,

Seb.

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