VOIP rookie. We have polycom handsets.Remote site has extreme x450 switches for lan connectivity. Remote sites are connected to main site via T1 on cisco 2811 routers. If I enable Auto qos voip on routers serial interfaces (Both SIdes) and CDP on polycom phones is that all that needs done to ensure QOS priority over the WAN for voip traffic?
That doesn't sound like it would work to me. I am not familiar with the extreme switches but I know that the 2811 routers will not see CDP enabled devices that are not directly (i.e. physically) connected to it. Of course, I didn't know that polycom phones can run CDP. So, maybe I am not the right guy to give advice here ;-)
I do think Polycom devices can be provisioned to mark QoS and if the extreme switch can preserve QoS then you can configure the 2811 to trust the QoS markings coming from the extreme switch. That is just the marking portion. The auto-qos feature on the 2811 should set up the LLQ/CBWFQ and I assume you have configured the scheduling/queuing on the extreme switch.
Basically, I think you will have some tweaking to do to get where you want to be. Sorry I couldn't be more specific.