trust dscp command at port plugged with AP

[interfacedy]

Hi we have two commands for trusting dscp at switch port connected to AP. One is auto qos trust dscp and another is mls qos trust dscp. What is difference between the two commands in this situation? I think both have the same the effect, but the first one can be modified. Am i right? Thanks

[Rasika Nayanajith · Accepted solution]

"MLS QoS" for IOS devices - Prior to 3850/9000 series. All newer switches by default trusting DSCP.

If you have IOS switches (29xx/35xx/37xx) series, then you have to configure QoS trust, otherwise it will by default rewrite to Best Effort (DSCP 0). Both commands you listed achieve the same thing.

HTH
Rasika
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[interfacedy]

Thanks Rasika for your great answer! When packet with dscp goes through a switch, as the switch port is dscp trusted, the packet dscp would not be changed. 

so the question is if only command mls qos trust dscp is used in the switch, when a packet with decp ef is received through switch port, the packet will get higher priority treatment without other commands? In other word, the switch has some default commands or machnism to make the packet higher priority treatment? 

[Rasika Nayanajith · Accepted solution]

If your switch model use MLQ QoS (Multi Layer Switch QoS), you have to enable QoS on the switch using "mls qos" CLI command. Then you can configure individual QoS commands to trust DSCP|COS, queuing, shaping, policing,etc. Once QoS enabled globally there will be certain default setting in each of those categories. rewrite DSCP to 0 is the default behavior. If you want to understand it in detail, I would suggest watch below Cisco live session (you can go to https://www.ciscolive.com/ to watch it)

Campus QoS Design-Simplified BRKCRS-2501 [2019-CLUS]

Here is a couple of slides from this presentation to explain points you interested.

Even with AutoQoS, you have to enable it globally "auto qos srnd4" & then you can use interface level auto qos commands to modify the default behavior.

HTH
Rasika
*** Pls rate all useful responses ***

[interfacedy]

Thank you Rasika! its good explanation!