Hi,
A lot depends on whether you are experiencing quality issues with your voice.
If you are, there's a bit to it (the solution) so it wouldn't be appropriate to suggest a particular config with the info that I have. But general areas you need to look into are:
* Low latency queuing (would apply on config between the switches)
* WRED (would apply on config between the switches)
* Call admission control (Apply on CA)
* Trust boundaries (apply on edge switches)
HTH,
Andres