authenticating through one ldap server that uses other ldap servers & active director
 

My problem is that I want to authenticate users through an LDAP server in front that verifies the users from other LDAP servers and Active Directory.
How can it be done? Is there a way like changing configuration files to authenticate from other servers. or any idea?
help will be greatly appriciated
thanks in advance

You'd setup replication servers. Like with openldap, slapd is the main stand-alone server listening, you'd then use slurpd to replicate from that host to another, etc.. www.openldap.org

Getting it to work with AD would be a whole other task, but I'm sure it's been easily done before. A quick google search might find some setups and configs that you could go by.