QoS on Nexus 5500

[George Thomas]

Hello,

I have a Nexus 5500 which is the core of our network and we have access layer switches uplinked to it. I know by default the qos markings will be trusted. 1. On a trunk uplink from an access layer switch to the Nexus, I have "mls qos trust dscp". Will the DSCP marking be preserved when it reaches the Nexus?

2. How do I do priortization of voice traffic on an uplink on Nexus based on DSCP EF?

Thanks in advance!

[Reza Sharifi]

Hi,

1-Yes, as long as you trusted on the access layer switch (which you are doing).

2-You would need to configure a class map

switch# configure terminal

switch(config)# class-map type qos match-any class_dscp

switch(config-cmap-qos)# match  dscp af21, af32

config guide:

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/qos/503_n1_1/cisco_nexus_5000_qos_config_gd_503_chapter3.html

HTH

[George Thomas]

Thank you Reza, once I match DSCP XX, will I be enable PFC for that specific traffic?

[Reza Sharifi]

Hi George,

According to the config guide

If a system class is configured with a no-drop             function, the              match cos             command serves an additional purpose. The switch sends the CoS value to the             adapter so that the adapter will apply a PFC pause for this CoS value.

I have never tested this, but I think the PFC funtion is done by default.

HTH