Hi Kristján,

The access vlan x and voice vlan y would be similar to do

switchport trunk enca dot1q
switchport trunk allow vlan x,y
switchport trunk native vlan x

So, the show inter trunk would not show the voice vlan "trunk"
interface, but it sure is there. So you would trust cos on both the
voice vlan config and the complete trunk port config.

alternatively you could trust device cisco-phone if available.

If the voice vlan config was not there no frames would be have the
dot1q add-on and hence no COS field to trust. You would trust trust
DSCP in that case.

/Ralph


2011/8/16 Kristján Ólafur Eðvarðsson <[email protected]>:
> I can´t believe that I am asking this but what the the heck :D
>
> A cisco phone connected to a switch.
>
> !
> switchport mode access
> switchport voice vlan x
> switchport access vlan x
> !
> I have somehow considered the phone to send COS layer
> 2 packets on the voice vlan because the phone is actually
> trunking (after negotiating voice vlan with cdp) data and user vlan.
> !
> However the port is in access mode (as it looks) and show int status shows 
> that clearly..
> !
> I have a question in my practice LAB that wants layer2 ports and interswitch 
> links to
> trust cos and layer3 interfaces to trust DSCP.
> !
> Am I not right to trust cos on the phone port ?
> even though it seems access it is sending COS layer2 tags on the packets 
> right ?
>
> Another bonus question if the phone didn´t have the switchport voice vlan
> but only a access VLAN it would sit on. Would that still be mls qos trust cos 
> ?
>
> regards. Kristjan
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