We need to prioritize VoIP traffic over a number of Catalyst 2955 and 2960 switches that are connected about 5-50 miles away from our corporate center via fiber. The switches will be no problem as I'll set all of the Mitel phones to have a CoS value of 5 and will implement Cisco EasyQoS on those switches.
My problem is with the ASA, that acts as a router on a stick to route between all of our VLANs. We have about 20 VLAN's, but only (3) will be needed for the phones. The problem is that the phones are part as the same VLAN's as the data connections, so I cannot prioritize simply by interface. So let's say I have VLAN 50, VLAN 51 and VLAN 52 that carries voice and data, and that these VLAN's are sub-interfaces.
How can I correctly implement QoS for the phones in this scenario?