I am using ssh auto login for transfering files between servers. I move RSA fingerprint to new server for preventing these warnings : REMOTE HOST IDENTIFICATION HAS CHANGED or confirming RSA key fingerprint Are you sure you want to continue connecting (yes/no).
Copy files under /etc/ssh directory to new server.
scp youroldserver:/etc/ssh/ssh_host_* /etc/ssh
You should move your ipadress to old server. If not you will get confirmation again.Or you can duplicate related entries in known_hosts file and change old ip adresses or hostname.