QoS default

[Charlie Grey]

if we enable mls Qos command on a C3560, by default, all ports are untrusted + COS override:dis + default COS:0.

if we have the below, what will be the QoS value at the egress?

Untagged frame (Access port connect PC) - at egress will be COS:0???

Tagged frame (Trunk port 802.1Q w COS:5) - at egress will be COS:5 or 0???

[Joseph W. Doherty]

I recall (?) for the 3560 (and 3750), the default, with mls QoS enabled, is untrusted ingress ports ToS and CoS are set to zero.

[Charlie Grey]

in that case, in what scenario is this parameter COS override:dis be used?

[Joseph W. Doherty]

I don't recall.  Not a feature I've ever used, especially I generally only use L3 ToS, not L2 CoS, as the former carries end-to-end, but the latter only useful with tagged frames, which often has a very limited life in the end-to-end path.

But if you have a link to Cisco's corresponding documentation, I might be able to "translate".