Hello everyone.
Well, I have a scenario with three LDAP servers. This scenario represents a practical structure of a multi-campus institution.

For example:
Each server of each campus has the following contexts instantiated name in a backend hdb:

Campus 1: dc = a, dc = institution, dc = org
Campus 2: dc = b, dc = institution, dc = org
Campus 3: dc = c, dc = institution, dc = org

Each campus only manages your server, but allows that queries to other remote servers. They must present themselves as a single directory, transparent to user queries.
I tried using the backend target with the suffix dc=institution,dc=org to perform a masking of the name.
In practice the target backend (server instantiated in the campus) is like this:

database meta
suffix "dc=institution,dc=org"

uri "ldap: / / localhost /dc=a"
idassert-bind  bindmethod=simple
rebind-as-user yes
suffixmassage "dc=institution,dc=org"  "dc=a"

# Remote Server - b
uri "ldap: / /"
idassert-bind  bindmethod=simple
                 binddn="cn = reader,dc = b"
                  credentials = "leitorb"
rebind-as-user yes
suffixmassage "dc=institution,dc=org"  "dc=b"
lastmod off

# Remote server - c
uri "ldap: / /"
idassert-bind  bindmethod=simple
                 binddn="cn=reader,dc = c"
                 credentials = "leitorc"
rebind-as-user yes
suffixmassage "dc=institution,dc = org"  "dc=b"
lastmod off

When performing a general consultation to  dc=institution,dc=org all data from the three campuses were merged and the query returned.
ldapsearch -x -D cn=reader,dc=a -W -b dc=institution,dc=org "cn=reader "

the result is:
cn = reader, dc = institution, dc = org
cn = reader, dc = institution, dc = org
cn = reader, dc = institution, dc = org

3 results appear, each encontraddo in three different bases. The problem is that have the same DN.

Assuming that this structure is used to authentication user and a user can log in at any institution, be it home or away, if any two users with uid=john (eg: uid=john,dc=a and uid=john,dc=b) when performing a search using the meta backend, duplicate the results appear.

Someone with experience in using the meta backend, give me a hint how to implement this scenario without causing an Replication DNs?
Suddenly a way to make the server does not store a new entry if it is equal to an existing (masquerading under the proxy target)?

The main objective of this implementation is to implement a distributed model that guarantees
1 - administrative independence for each campus (just write in your base, but read all)
2 - Allow users to authenticate to the system, inside or outside their home institution.

Finally, it would be possible to use the backend relay, after which the main role of the backend?

Thanks in advance.