Set speed/duplex on trunk port when using AutoQOS on a Cisco 3850 switch

[Charlie Jones]

I have an office where we replaced their existing switches with 3850 switches and we are using Auto QOS.  Once the replacement was done, we started to see discarded traffic from our NMS.  In troubleshooting the issue, I noticed on some of the trunks class-default traffic was being dropped.  I compared the policies from one site to another, and they are identical.  The only difference I have been able to find is that in the office where we are having the discards, none of the trunks between switches are locked to 1000/full.   Can this affect QOS if they are set to auto/auto?  I went through some AutoQOS info from Cisco and they don't talk about setting port speed/duplex.

Thanks.

[Reza Sharifi]

Port speed and duplex does not effect QOS. For testing you can remove the QOS config from the ports and see if you still have droops.

HTH