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QoS default

Charlie Grey
Level 1
Level 1

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???

3 Replies 3

Joseph W. Doherty
Hall of Fame
Hall of Fame

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

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

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".