For TLS 1.2 cipher Suite AES256-GCM-SHA384, RSA is KEX(key exchagne algorithm). As per standards of RSA Diffie Hellman KEX, after 'ServerHello' message client gets server certificate and it generates a 48 byte random number which is 'pre master secret' and sends it to server. This ensures both have setup pre master secret.
Are client.random and server.random anyway related(mathemetically) to pre master secret?
As per my understanding (after researching on web), server.random prevents handshake replay attack in ECDH. How is RSAKEX preventing handshake replay attack?
Are they only significant after master secret generation and succeeding steps, but not in preventing handshake replay attack?