QoS testing

I'm after a bit of help / advise, though I realise that QoS is one hell of a rabbit hole to fall down and I might be a bit out of my depth...!

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I'm testing the QoS values on a local switch are being trusted, so running a ping -v 184 from one PC to another. If I run wireshark from a desktop & look at the pings from that PC, I can see the dscp vlaue set to EF as I expected. However is I look at the pings from a different PC to mine with the same -v 184 value set I see a DSCP of CS, i.e. nothing set 0x00

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The switch has mls qos turned on and all the ports on it are set to mls qost trust dscp.

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If I set an extended ping going with the ToS value set to 160 / 184 etc then I can see on the local desktop running wireshark that the DSCP vlaue is set correctly.

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I don't understand why the dscp value is being stripped out from the other desktop device though if the ports are set to trust dscp?

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I was hoping that once I confirmed it's working locally I can start sending the pings from further afield and test the end to end QoS connectivity of all our sites.