RHEL AS 3 is NIS server, but cannot login using NIS id from AIX and HP-Unix NIS clients

[unix syzadmin]

   Hi,

We have a RHEL AS 3 in our lab serving as NIS server. We have Linux,
Solaris, hp-unix & AIX NIS clients.

I can use NIS id to login from Linux and Solaris, but cannot login from AIX
and HP-Unix.

Does linux have any limitation or I am surely missing some configuration.
Please suggest or point me in the right direction.

Thanks & Regards,
-GnanaShekar-