NIS to LDAP Migration

Hi ,
      This question is not directly Tru64.
I am in process of migrating users to LDAP (Openldap 2.3.x in the test
environment) . We have 60 normal users and plus we get 20 -30 new students
every year. I have some workstations and servers running Tru64 4.0F and 5.0
which cannot be upgraded . my question
How can I handle User Authentification on theses machines ?

I have thought of two ways as I could not find any opensource gateway(LDAP
to NIS)tool.

option1
 Maintain  NIS and openldap environment separately (Since 90 % new users
only require ldap access) I only have to create NIS accounts for users who
really need access to these machines.

option 2
Is same as above Just that I still continue to use NIS for user creation
and sync with openldap regularly.


I wanted to know how other admins have dealt  with similar situation think
and is there a tool available to keep both the environment in sync?

Thanks in advance
Wishing all a healthy and successful 2007

yogesh