The first step is to generate public and private keys for SSH. There are two versions of the SSH protocol; version 1 uses RSA and version 2 uses DSA, so we will create both types of keys to ensure that SSH can use either version. The ssh-keygen program will generate public and private keys of either type depending upon the parameters passed to it.
From ORACLE DATABASE 11gR2, this process is automated in OUI itself. You can find the script "sshUserSetup.sh" in the 11gR2 grid media.
You can use this script for ssh setup in releases prior to 11gR2 RAC.
Note : Password only 4 times
Note : Enter password carefully
[oracle@rac1 sshsetup]$ ssh rac1 date;hostname
Sun Aug 14 09:41:33 IST 2010
[oracle@rac1 sshsetup]$ ssh rac2 date;hostname
Sun Aug 14 09:41:39 IST 2010
1. ssh both public hostname
2. ssh both private hostname
3. ssh both public ip address
4. ssh both Private ip address
Screen shots showing how this is implemented in 11gR2 RAC ....
Hope it helps ...