Hello Bilal
You can't have CVP in cluster for centralized configuration. You need to configure each of them seperately.
For the load ballancing,
For Call Signalling, you can use Gatekeeper if you use H323. And you can use SIP Proxy Server like CUPS or CUSP for load balancing.
Since VXML server uses HTTP, you can CSS to do the load balancing.
Hope this helps.
thanks
- abu