on an ingress port on switch A I set the COS value to 5 which is map to dscp 46 (I can check that when I change the CoS value the dscp value changes according to the cos-dscp map). On switch B (802.1Q trunk between the switches), I now look at the incoming packet. When on switch B I set the incoming Trunk to trust DSCP, i can see the dscp value set in switch A. But if I code the trunk as trust COS and look a tthe dscp value in the packet, I can see dscp=0 which means that the Cos was also set to 0.
It looks like switch 1 uses cos-dscp and dscp-cos maps internally but does not tag the ougoing packet at L2. IS this normal ?
I tested between 3550 and 2950.