ssh2-keygen trust issue

I have two systems SysA & SysB having the same userid sharing the home directory via NFS mount.

I need to know the steps to setup ssh trust between these two systems given that both share the home dir.

I have tried all the steps to generate the keys & then creating identification & authorization files, but no luck..may be I am missing on something.

Thanks in advance.

I forgot to mention that the userid is using NIS authentication.

Make sure that you have "UsePAM yes" in the sshd config files. If that's not it tell us what OS and what ssh you are using.