6500 hardware qos trust question

[paul amaral]

I have a question which im unsure of, on the 6500 i know i can set mls qos trust to cos or dscp since I dont have any trunks configured on that switch that i want to trust cos most of my ports trust dscp instead. The question is will packets coming in or going out at L3 with the TOS bits set get placed in the correct in/out queue. For example if a packet comes in on a port with a mls qos trust dscp and has the TOS set to XX will this XX get mapped to the correct COS value based on the default dscp to cos map and end up going out the correct queue which handles that specific COS number?

I mainly asked this because i saw the following on the cisco site and again im suing dscp trust and not cos.

Weighted Round Robin (WRR), Deficit Weighted Round Robin (DWRR) and Shaped Round Robin (SRR). WRED and all the Round Robin scheduling options use the priority tag (CoS) inside an Ethernet frame to provide enhanced buffer management and outbound scheduling.

thanks, Paul

[p.mcgowan]

the following command will show the cos-dscp mappings;

show mls qos maps cos-dscp

The following doc is very useful for troubleshooting QoS;

http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008074d6b1.shtml

please rate if useful

[paul amaral]

i had time to research this and it looks like if your incoming trust is set to dscp and not cos you will not be able to specify what marked packets use what input queue, however if your  incoming trust is set to dscp this will cause the packet to be assigned an internal dscp that will be used through the switch and from the dscp a cos value will be derived when the packet is sent to the output queue. So you get no incoming benefit just outgoing from what i understand.

Hope this helps someone, paul