3550 "mls qos cos override" and "mls qos trust cos"

[teru-lei]

Hi all,

In 3550, when use "mls qos trust cos" the swith with trust the cos value of the frame in that port. If I don't use it, will the switch override the cos value? If it will, why should we use "mls qos cos override" command? Can anyone tell me? Thank You!

Best Regards

Teru Lei

[bbranch]

The "mls qos trust qos" command instructs the switch to honour the incoming cos value in the packet. The "mls qos cos " command intructs the switch to assign a COS value to any untagged packet and the "mls qos cos override" command instructs the switch to replace any cos received on a trusted port (a tagged packet) with the cos defined in the command - this overrides the default trust state of the port by replacing the existing cos value with a new one. This allows greater flexibility by allowing the trust state of a port to be overridden on a port by port basis.