thanks Robert; we followed the instructions mentioned in http://thelastpickle.com/blog/2015/09/30/hardening-cassandra -step-by-step-part-1-server-to-server.html. It worked great.
Due to the security policies in our company, we were asked to use 3rd party signed certs. Since we'll require to manage 100's of individual certs, we wanted to know if there is a work around with a generic keystore and truststore. thanks Sai