Use the "auto qos voip trust" on the ethernet port of the ROUTER (see example below). You don't need to mark the trunk port on the switch that connects to the router, as all traffic headed to the voice vlan on the router (from phones, etc.,) will be prioritized as they come in their respective ports. If you prioritize the router (as I show below), all outbound traffic leaving the router will be prioritized properly as well.
To explain it another way, the router will do the prioritizing for you, so you don't need to have the switch prioritize traffic on the trunk.
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!
interface FastEthernet0/0
description Trunk to switch
no ip address
duplex auto
speed auto
auto qos voip trust
service-policy output AutoQoS-Policy-Trust
!
interface FastEthernet0/0.10
description Data VLAN 10
encapsulation dot1Q 10
ip address 192.168.10.1 255.255.255.0
no snmp trap link-status
!
interface FastEthernet0/0.20
description Voice VLAN 20
encapsulation dot1Q 20
ip address 192.168.20.1 255.255.255.0
no snmp trap link-status
!
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Later,
Go0se